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BRITL    574.  19.H38    c.  1 
HENDERSON    #    FITNESS    OF 
ENVIRONMENT 


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THE  FITNESS 
OF  THE  ENVIRONMENT 


THE  MACMILLAN  COMPANY 

NEW  YORK    .    BOSTON   •    CHICAGO 
DALLAS    •    SAN    FRANCISCO 

MACMILLAN  &   CO.,  Limited 

LONDON  •    BOMBAY  •    CALCUTTA 
MELBOURNE 

THE  MACMILLAN  CO.  OF  CANADA,  Ltd. 

TORONTO 


THE  FITNESS 
OF  THE   ENVIRONMENT 

AN   INQUIRY 

INTO    THE   BIOLOGICAL   SIGNIFICANCE    OF 

THE   PROPERTIES   OF   MATTER 


BY 

LAWRENCE  J.  HENDERSON 

ASSISTANT    PROFESSOR   OF   BIOLOGICAL   CHEMISTRY 
IN  HARVARD   UNIVERSITY 


IN   PAET   DELIVERED   AS   LECTURES   IN   THE 
LOWELL   INSTITUTE,    FEBRUARY,    1913 


THE  MACMILLAN  COMPANY 
1927 

All  rights  reserved 


PRINTED    IN    THE    T7NITED    STATES    OF   AMERICA 


Copyright,  1913, 

Bt  the  macmillan  company. 

Set  up  and  electrotyped.     Published  February,  1913. 


J.  8.  Cushing  Co.  —  Berwick  &  Smith  Co. 
Norwood,  Mass.,  U.S.A. 


PREFACE 

Darwinian  fitness  is  compounded  of  a 
mutual  relationship  between  the  organism 
and  the  environment.  Of  this,  fitness  of  en- 
vironment is  quite  as  essential  a  component  as 
the  fitness  which  arises  in  the  process  of  or- 
ganic evolution  ;  and  in  fundamental  charac- 
teristics the  actual  environment  is  the  fittest 
possible  abode  of  life.  Such  is  the  thesis 
which  the  present  volume  seeks  to  estabhsh. 
This  is  not  a  novel  hypothesis.  In  rudimen- 
tary form  it  has  already  a  long  history  behind 
it,  and  it  was  a  familiar  doctrine  in  the  early 
nineteenth  century.  It  presents  itself  anew 
as  a  result  of  the  recent  growth  of  the  science 
of  physical  chemistry. 

About  fifteen  years  ago  I  first  became  inter- 
ested in  the  connection  between  physical  and 
chemical  properties  of  simple  substances  and 
the  organic  functions  which  they  serve.  At 
that  time  the  apphcations  of  the  new  physical 
chemistry  to  physiology  were  only  just  begin- 
ning, and  the  older  speculations  of  natural 
theology  upon  such  subjects  had  long  since 


vi  PREFACE 

passed  into  oblivion.  It  was  a  time  of  very 
little  interest  in  such  matters,  for  many  lines 
of  development  of  natural  science  during  the 
preceding  quarter  century  had  conspired  to 
divert  attention  to  other  problems.  The  im- 
mediate occasion  of  my  interest  was,  I  well 
remember,  the  chance  reading  of  Maly's  im- 
portant but  almost  forgotten  papers  upon 
the  diffusion  and  dialysis  of  phosphates,  re- 
counting phenomena  which,  in  the  light  of  the 
modern  theory  of  ionization,  appeared  simple 
enough,  though  to  their  discoverer  they  had 
been  in  some  respects  inexplicable.  A  series 
of  researches  have  grown  out  of  this  interest, 
and  since  that  time,  whenever  freedom  has 
permitted,  I  have  been  occupied  with  various 
aspects  of  the  problem  of  the  neutrality  or 
faint  alkalinity  of  the  organism.  For  it  soon 
appeared  that  the  key  to  the  peculiar  condi- 
tions of  equilibrium  between  acids  and  bases 
in  blood  and  protoplasm  is  to  be  found  in  such 
characteristics  of  phosphate  solutions  as  Maly 
had  observed,  and  in  like  behavior  of  similar 
solutions  containing  carbonic  acid.  When  at 
length  it  became  possible  quantitatively  to 
describe  the  chemical  equilibra  in  such  sys- 
tems, it  w^as  at  once  clear  that,  of  all  known 
substances,  phosphoric  acid  and  carbonic  acid 
possess  the  greatest  power  of  automatic  regu- 


PREFACE  vii 

lation  of  neutrality  (the  concentration  of  ion- 
ized hydrogen  and  hydroxyl  at  the  neutral 
point). 

One  does  not  Hke  to  accept  a  fact  of  such 
far-reaching  importance  as  mere  chance,  and 
yet  no  other  explanation  was  at  hand.  For, 
after  the  briefest  consideration,  it  was  obvious 
that  here,  at  least,  natural  selection  could  not 
be  involved.  But  it  was  also  certain  that  this 
is  no  unique  instance  of  a  property  of  a  simple 
substance  automatically  serving  a  very  useful 
purpose  in  the  processes  of  life.  Like  every 
one  who  has  received  a  chemical  training,  I 
was  vaguely  conscious  of  numerous  other  simi- 
lar cases  ;  like  every  one  who  has  any  acquaint- 
ance with  the  general  properties  of  matter,  I 
knew  that  the  remarkable  thermal  properties 
of  water  are  of  great  importance  to  living  or- 
ganisms. However,  in  spite  of  the  fact  that 
I  had  been  brought  face  to  face  with  a  definite 
problem  whose  solution  now  appears  to  be 
perfectly  patent,  so  great  is  the  natural  inertia 
of  the  mind,  and  so  firmly  estabhshed  was  the 
belief  that  natural  selection  is,  on  the  whole, 
quite  adequate  to  account  for  biological  fit- 
ness, that  for  a  number  of  years  I  made  no 
further  progress. 

Then,  finally,  after  a  long  period  of  uncer- 
tainty, came  the  realization  of  the  reciprocal 


viii  PREFACE 

character  of  Darwinian  fitness,  and  at  once 
the  whole  difficulty  was  resolved.  On  all 
sides  instances  of  environmental  fitness  were 
manifest,  and  casual  search  brought  many 
other  cases  to  light.  The  forgotten  literature 
of  natural  theology  is  crammed  with  illustra- 
tions, and  the  recent  biological  developments 
of  physical  chemistry  have  provided  still 
others.  It  is,  indeed,  a  very  curious  episode 
in  the  history  of  thought  that  these  well- 
known  facts  should  have  been  so  long  forgot- 
ten or  misconstrued.  But,  though  forgotten, 
they  have,  so  to  speak,  lain  dormant  in  the 
minds  of  physical  scientists,  and  I  have  found 
both  chemists  and  physicists  ready  to  accept 
them  without  hesitation.  In  the  following 
pages  an  attempt  has  been  made  to  collect 
and  to  interpret  such  facts,  in  so  far  as  they 
arise  among  the  compounds  of  carbon,  hydro- 
gen, and  oxygen,  especially  in  the  cases  of 
water  and  carbonic  acid.  This  restriction  has 
been  adopted  in  order  to  facilitate  the  logical 
discussion,  and  it  should  be  borne  in  mind 
that  other  phenomena,  dependent  upon  the 
properties  of  other  substances,  such  as  the 
above-mentioned  characteristics  of  phosphate 
solutions,  belong  in  the  same  category. 

The  argument  which  has  been  thus  devel- 
oped is  comparatively  rigid  and  closely  woven. 


PREFACE  ix 

That  is,  perhaps,  in  some  respects  unfortunate, 
because  the  impression  which  must  be  pro- 
duced is  unhke  that  of  the  facts  themselves, 
and  the  argument  is  certainly  very  different 
from  the  mental  process  through  which  I  have 
myself  passed  in  reaching  the  conclusion.  But 
it  would  be  very  difficult  indeed  in  any  other 
manner  to  set  forth  all  the  necessary  consid- 
erations, so  that  they  should  be  intelligible  to 
any  one  but  the  physico-chemical  biologist, 
and  on  the  whole  there  seems  to  be  no  choice 
but  to  follow  a  logical  rather  than  a  descrip- 
tive method.  The  reader  will  find,  however, 
that  in  the  main  Chapters  III,  IV,  V,  and 
VI  are  concerned  with  evidence  alone.  This 
taken  together,  as  a  whole,  is  the  only  true 
ground  for  a  conclusion,  and  it  is  upon  the 
general  character  of  the  evidence  rather  than 
upon  an  argument  which  only  serves  as  a 
means  to  the  end  that  I  should  wish  to  rest 
my  case.  To  many,  on  the  other  hand,  as  to 
any  biologist  who  may  not  care  to  examine 
the  difficult  facts  of  physics  and  chemistry, 
Chapters  I,  II,  VII,  and  VIII  will  be  sufficient 
to  explain  both  the  purpose  of  the  book  and 
the  outcome  of  the  investigation. 

There  has  been  a  constant  effort  to  restrict  all 
discussions  to  the  utmost,  because  at  the  pres- 
ent time  encyclopaedic  handbooks  covering  all 


X  PREFACE 

departments  of  science  have  so  multiplied  that 
hardly  any  facts  or  theories  which  come  within 
the  scope  of  this  work  are  inaccessible  to  the 
general  reader.  On  the  other  hand,  it  has 
been  deemed  necessary  to  explain  every  sub- 
ject as  it  has  arisen,  for  many  of  the  readers 
of  this  volume  will  perhaps  be  unfamiliar  even 
with  the  rudiments  of  all  the  departments  of 
science  which  have  necessarily  been  touched 
upon. 

Much  of  the  content  of  the  following  pages 
has  already  been  set  forth  in  lectures.  The 
general  conclusion  was  presented  last  February 
to  the  members  of  the  Harvard  Seminary  of 
Logic ;  later  in  the  academic  year  I  delivered 
the  substance  of  the  book  as  part  of  a  college 
course  to  my  students  of  biological  chemistry 
in  Harvard  College. 

I  am  indebted  to  many  of  my  colleagues  in 
Harvard  for  valuable  assistance,  criticism, 
and  expressions  of  opinion.  Without  such 
assurances  that  I  have  not  fallen  into  gross 
blunders,  and  that  the  conclusions  appear  rea- 
sonable to  experienced  men  of  science,  I  should 
not  have  dared  to  undertake  a  task  which 
overtaxes  my  knowledge,  or  positively  to  as- 
sert a  proposition  which  is  in  conflict  with 
much  of  the  scientific  thought  of  the  last  half 
century.    Especial  thanks  are  due  to  Professor 


PREFACE  xi 

Josiah  Royce.  His  learning  and  generosity 
have  in  the  past  aided  me  to  reach  an  under- 
standing of  the  philosophical  problems  of  sci- 
ence, and  in  the  preparation  of  this  book  they 
have  repeatedly  guided  me  aright. 

Seal  Harbor,  Maine, 
August,  1912. 


CONTENTS 
CHAPTER  I 

PAGS 

FITNESS 1 

I.    Purpose  and  Order 1 

II.     Fitness 4 

III.  The  Environment 8 

A.  Matter 8 

B.  Energy 15 

C.  Space  and  Time 19 

IV.  The  Organism 21 

A.  Metabolism 24 

B.  Organic  Chemistry 28 

C.  The  Characteristics  of  Life    ....  30 
V.    The  Problem 36 


CHAPTER  II 

THE  ENVIRONMENT 38 

I.     Astronomy 38 

II,    Possible  Environments 49 

III.  Geophysics 52 

IV.  The  Atmosphere 55 

V.     General  Cosmographical  Conclusions      .        .  60 

VI.    The  Primary   Constituents   of  the  ENvraoN- 

ment 61 

VII.    The  Ultimate  Problem 63 

VIII.     The  Method  of  Solution 67 

xiii 


xiv  CONTENTS 

CHAPTER  III 

PA&B 

WATER 72 

I.    Thermal  Properties 80 

A.  Specific  Heat 80 

B.  Latent  Heat 92 

C.  Thermal  Conductivity 106 

D.  Expansion  before  Freezing       ....  106 
II.    The  Action  of  Water  upon  Other  Substances  110 

A.  Water  as  a  Solvent  .         .         .         .         .         .  Ill 

B.  Ionization 118 

C.  Surface  Tension 126 


CHAPTER  IV 

CARBONIC  ACID 133 

I.    Solubility 136 

II.    Acidity 140 


CHAPTER  V 

THE  OCEAN 164 

I.    The  Regulation  of  Physico-chemical  Conditions  164 

II.    The  Circulation  of  Water 180 

III.    The  Ocean  as  Environment         .        .        ,        .  183 


CHAPTER  VI 

THE  CHEMISTRY  OF  THE  THREE  ELEMENTS        .  191 

I.    Organic  Chemistry 191 

A.  Valence 196 

B.  Hydrocarbons 197 


CONTENTS  XV 

PAGE 

C.  Compounds  of  Carbon,  Hydrogen,  and  Oxygen  202 

D.  Other  Organic  Compounds       ....  208 

E.  The  Characteristics  of  Organic  Substances       .  209 

F.  The  Sugars 222 

G.  Hydrolysis 232 

n.     Inorganic  Chemistry 237 

III.    Thermochemistry    .......  243 


CHAPTER  VII 

THE  ARGUMENT 249 

I.     Analysis  of  the  Evidence 250 

II.    The  Exhaustiveness  of  the  Treatment     .        .    253 
III.    Summary  .        .        .        .        .        «        .        .267 


CHAPTER  VIII 

LIFE  AND  THE  COSMOS  ......  274 

I.    The  Significance  of  Fitness         .        o        .        .  274 

II.    Vitalism 282 

A.  The  Vitalism  of  Bergson 293 

B.  Vitalism  and  Teleology 298 

III.     Cosmic  Evolution 301 

A.  The  Periodic  System 303 

B.  Teleology 305 


CHAPTER  I 
FITNESS 

I 

PURPOSE  AND  ORDER 

IDEAS  of  purpose  and  order  are  among 
the  first  concepts  regarding  their  en- 
vironment which  appear,  as  vague  antici- 
pations of  philosophy  and  science,  in  the 
minds  of  men.  In  truth,  when  the  manifold 
phenomena  and  experiences  of  daily  life 
stored  in  the  memory  are  critically  scruti- 
nized, purpose  and  order  seem  naturally  to 
suggest  themselves  as  explanations  of  the 
universe.  Day  and  night,  the  changing  but 
recurring  seasons,  the  fertilizing  sunshine 
and  rain,  the  flight  of  birds,  the  powers  of 
the  human  hand,  and  all  the  beauties  and 
mysteries  of  nature  cannot  fail  of  such  in- 
terpretation by  the  simple  and  untrained 
mind.  Alike  anthropology  and  the  history 
of  primitive  civilizations  bear  witness  to  this 
natural  tendency  of  thought.    Such  ideas  pre- 


2        THE  FITNESS  OF  THE   ENVIRONMENT 

cede  exact  knowledge  and  civilization,  and 
arise  spontaneously  among  savage  peoples. 
They  are  the  solvent  of  the  chaos,  as  which 
the  outer  world  first  presents  itself  to  our 
eyes  and  hands,  and  they  are  the  fabric  of 
all  theologies. 

As  civilization  has  progressed,  these  early 
hypotheses  have  received  endless  criticism, 
and  their  definition  has  been  continually 
sharpened.  Meantime  natural  science  has 
sought  and  provided  ever  more  accurate 
accounts  of  the  phenomena  which  first  sug- 
gested them  to  man,  and  of  countless  other 
forms  and  transformations  of  matter  and 
energy,  and  the  discovery  of  laws  of  nature 
has  steadily  changed  once  quite  mysterious 
order  and  purpose  into  the  plainest  of  neces- 
sary results. 

Upon  the  advent  of  modern  science  order 
speedily  began  to  receive  its  true  account 
when,  after  only  a  half  century  of  progress, 
dynamics  through  Newton  provided  a  formu- 
lation of  the  laws  which  govern  the  most 
striking  of  all  the  orderly  phenomena  of 
nature.^     Since    Newton's   day  the    explana- 

^  **  Die  Newton'schen  Principien  sind  geniigend,  um  ohne 
Hinzuziehung  eines  neuen  Princips  jeden  praktisch  vorkom- 
menden  mechanischen  Fall,  ob  derselbe  nun  der  Statik  oder 
der  Dynamik  angehort,  zu  durchschauen.  Wenn  sich  hierbei 
Schwierigkeiten  ergeben,  so  sind  dieselben  immer  nur  ma  the- 


FITNESS  3 

tion  of  natural  order  as  the  automatic  result 
of  natural  law  has  not  ceased,  and  at  length 
has  become  so  nearly  complete  that  the  ap- 
pearance of  order  under  any  circumstances  is 
now  taken  as  proof  of  the  existence  of  a  law. 

The  fate  of  the  hypothesis  of  purpose  in 
nature  has  been  less  simple,  because  the  dis- 
covery of  law,  or  even  of  the  possibility  of 
law,  underlying  adaptation  and  fitness  was 
more  difficult.  Until  the  middle  of  the  nine- 
teenth century  the  countless  adaptations  of 
organisms  to  the  environment  and  the  mani- 
fest fitness  of  nature  for  the  activities  of 
living  things  seemed  to  many  biologists  only 
explicable  as  the  result  of  some  directing 
force. ^     Even   skeptics   were  nearly  or   quite 

mathischer  (formeller)  und  keineswegs  mehr  principieller 
Natur."  —  Mach,  "Die  Mechanik  in  Ihrer  Entwickelung 
Historisch-Kritisch  Dargestellt."    Leipzig,  1897, 3d  ed., p.  257. 

"  Dann  hat  er  auch  die  Aufstellung  der  heute  angenom- 
men  Prineipien  der  Mechanik  zu  einem  Abschluss  gebracht." 
—  Mach,  ibid.  p.  181. 

^  See  for  example  that  remarkable  series  of  works,  the 
Bridgewater  Treatises  "On  the  Power,  Wisdom,  and  Goodness 
of  God,  as  manifested  in  the  Creation ;  illustrating  such  work 
by  all  reasonable  arguments,  as  for  instance  the  variety  and 
formation  of  God's  creatures  in  the  animal,  vegetable,  and 
mineral  kingdoms;  the  effect  of  digestion,  and  thereby  of 
conversion;  the  construction  of  the  hand  of  man,  and  an 
infinite  variety  of  other  arguments;  as  also  by  discoveries 
ancient  and  modern,  in  arts,  sciences,  and  the  whole  extent 
of  literature."  —  Whewell,  "Astronomy  and  General  Phys- 


4        THE  FITNESS  OF  THE  ENVIRONMENT 

unable,  however  strong  their  desire,  to  ac- 
count for  the  facts  with  a  plausible  theory. 
The  dogma  of  final  causes  had  led  a  thou- 
sand times  to  the  truth  by  teaching  the 
investigator  that  the  true  description  of  an 
organ  or  physiological  process  was  to  be  found 
in  its  utility  to  the  organism  as  a  whole. 
Such  considerations  were  far  too  numerous 
and  too  patent  for  science  to  shirk  some 
explanation,  and  the  only  weighty  explana- 
tion at  hand  seemed  the  teleological  one. 

n 

FITNESS 

With  a  suddenness  which  to  many  seemed 
catastrophic  Darwin's  hypothesis  of  natural 
selection  changed  the  whole  aspect  of  the 
problem.  Law  appeared  as  the  basis  of 
purpose  just  as  it  had  appeared  as  the  basis  of 
order,  and  adaptations  became,  in  the  judg- 
ment of  most  men,  the  necessary  results  of 
an  automatic  process.  To-day,  after  a  half 
century,  there  is  no  longer  room  for  doubt 
that  the  fitness  of  organic  beings  for  their  life 
in  the  world  has  been  won  in  whole  or  in  part 

ics  Considered  with  Reference  to  Natural  Theology."  Lon- 
don, 1834,  4th  ed.,  p.  ix. 

To  this  series  such  men  as  Whewell  and  Sif  Charles  Bell 
contributed. 


FITNESS  5 

by  an  almost  infinite  series  of  adaptations  of 
life  to  its  environment,  whereby,  through  a 
corresponding  series  of  transformations,  pres- 
ent complexity  has  grown  out  of  former  sim- 
plicity.^ 

The  great  and  fruitful  ideas  which  Darwin 
brought  to  the  attention  of  the  whole  world 
have  long  since  been  incorporated  into  hu- 
man thought.  Not  the  least  important 
among  them  is  the  new  scientific  concept  of 
fitness,  as  it  emerges  from  the  discussion  of 
natural  selection.  Before  Darwin,  this  concept 
possessed  all  the  vagueness  of  an  idea  which, 
though  in  part  founded  on  observation,  was 
not  to  be  explained  with  the  help  of  existing 
scientific  theories.  But  although  Darwin's 
fitness  involves  that  which  fits  and  that  which 
is  fitted,  or  more  correctly  a  reciprocal  rela- 
tionship, it  has  been  the  habit  of  biologists 
since  Darwin  to  consider  only  the  adaptations 
of  the  living  organism  to  the  environment.^ 

^  The  ideas  which  are  associated  with  the  names  of  de 
Vries,  as  well  as  the  very  different  hypotheses  of  Driesch, 
Bergson,  and  others  are,  of  course,  concerned  with  the  manner, 
not  with  the  fact  of  adaptation  and  organic  evolution. 

2  Far  different  was  the  earlier  point  of  view.  An  examina- 
tion of  Whewell's  Bridgewater  Treatise  at  once  reveals  im- 
portant, if  often  fallacious,  discussions  of  environmental  fit- 
ness; e.g.  "It  has  been  shown  in  the  preceding  chapters  that 
a  great  number  of  quantities  and  laws  appear  to  have  been 
selected  in  the  construction  of  the  universe ;   and  that  by  the 


6         THE  FITNESS  OF  THE  ENVIRONMENT 

For  them,  in  fact,  the  environment,  in  its 
past,  present,  and  future,  has  been  an  inde- 
pendent variable,  and  it  has  not  entered  into 
any  of  the  modern  speculations  to  consider 
if  by  chance  the  material  universe  also  may 
be  subjected  to  laws  which  are  in  the  largest 
sense  important  in  organic  evolution.  Yet 
fitness  there  must  be,  in  environment  as  well 
as  in  the  organism.  How,  for  example,  could 
man  adapt  his  civilization  to  water  power  if 
no  water  power  existed  within  his  reach  ? 

adjustment  to  each  other  of  the  magnitudes  and  laws  thus 
selected,  the  constitution  of  the  world  is  what  we  find  it,  and 
is  fitted  for  the  support  of  vegetables  and  animals  in  a  manner 
in  which  it  could  not  have  been,  if  the  properties  and  quan- 
tities of  the  elements  had  been  different  from  what  they  are. 
We  shall  here  recapitulate  the  principal  of  the  laws  and 
magnitudes  to  which  this  conclusion  has  been  shown  to 
apply. 

1.  The  Length  of  the  Year,  which  depends  on  the  force  of 
the  attraction  of  the  sun,  and  its  distance  from  the  earth. 

2.  The  Length  of  the  Day. 

3.  The  Mass  of  the  Earth,  which  depends  on  its  magni- 
tude and  density. 

4.  The  Magnitude  of  the  Ocean. 

5.  The  Magnitude  of  the  Atmosphere. 

6.  The  Law  and  Rate  of   the  Conducting  Power  of  the 
Earth. 

7.  The    Law   and    Rate  of  the  Radiating  Power  of  the 
Earth. 

8.  The  Law  and  Rate  of  the  Expansion  of  Water  by  Heat. 

9.  The  Law  and  Rate  of  the  Expansion  of  Water  by  Cold, 
below  40  degrees. 


FITNESS  7 

At  first  sight  it  may  well  seem  that  inquiry 
into  such  a  problem  must  end  unsuccessfully 
in  vague  and  unprofitable  guesses.  Indeed 
the  past  has  brought  forth  no  lack  of  such  vain 
attempts,  usually  guided  by  a  devotion  to 
the  doctrine  of  design  in  the  service  of  the- 
ology. Yet  other  sciences  have  grown  since 
1859,  and  physical  and  chemical  data  in 
abundance  are  now  at  hand  to  aid  in  a  recon- 
sideration   of    the    environment's    fitness,    if 

10.  The  Law  and  Quantity  of  the  Expansion  of  Water  by 
Freezing. 

11.  The  Quantity  of  Latent  Heat  absorbed  in  Thawing. 

12.  The  Quantity  of  Latent  Heat  absorbed  in  Evapora- 
tion. 

13.  The  Law  and  Rate  of  Evaporation  with  regard  to 
Heat. 

14.  The  Law  and  Rate  of  the  Expansion  of  Air  by  Heat. 

15.  The  Quantity  of  Heat  absorbed  in  the  Expansion  of 
Air  by  Heat. 

16.  The  Law  and  Rate  of  the  Passage  of  Aqueous  Vapor 
through  Air. 

17.  The  Laws  of  Electricity;  its  relations  to  Air  and 
Moisture. 

18.  The  Fluidity,  Density,  and  Elasticity  of  the  Air,  by 
means  of  which  its  vibrations  produce  Sound. 

19.  The  Fluidity,  Density,  and  Elasticity  of  the  Ether, 
by  means  of  which  its  vibrations  produce  Light."  —  Whe- 
WELL,  "Astronomy  and  General  Physics  Considered  with 
Reference  to  Natural  Theology."  London,  1834,  4th  ed., 
pp.  141-143. 

It  is  hard  to  understand  how  such  ideas  could  have  fallen 
mto  oblivion. 


8         THE  FITNESS  OF  THE  ENVIRONMENT 

such  exist.  Clearly  it  is  well  to  seek  among 
these  data  for  a  more  precise  formulation  of 
the  problem,  which  may  then  perchance  lead 
to  some  more  ambitious  quest,  or  at  least  to 
new  understanding  of  the  old  failure. 

Ill 

THE  ENVIRONMENT 

The  world  of  our  senses  is  a  world  of  matter 
and  energy,  space  and  time.  After  centuries 
of  philosophical  and  scientific  study,  these, 
the  very  logical  elements  of  science,  are  no 
doubt  still  without  a  final  description.  None 
the  less  is  there  sound  foundation  for  the 
belief  that  our  preliminary  accounts  of  all 
four  possess  completeness  in  some  respects 
and  for  certain  purposes.  Nor  are  we  to-day 
less  confident  of  the  finality  of  some  of  our 
ideas  regarding  the  nature  of  life  and  the  vital 
processes,  as  they  exist  in  this  world.  But 
both  of  these  conclusions  call  for  further 
consideration. 


MATTER 

Many  facts  contribute  to  the  belief,  uni- 
versal among  chemists,  that  the  known  ele- 
ments constitute  by  far  the  greatest  part  of 


FITNESS  9 

a  system  of  materials  out  of  which  the  uni- 
verse is  formed,  within  which  all  chemical 
changes  (except  certain  phenomena  of  radium 
and  a  few  other  anomalies,  including  perhaps 
unknown  changes  in  the  interiors  of  the 
celestial  bodies)  take  place. 

It  is  certain  that  nearly  all  the  chemical 
transformations  upon  the  earth  consist  of 
rearrangements  of  the  atoms  of  the  known 
elements.  A  century  and  a  half  of  scientific 
chemistry  guarantee  that  conclusion  with  a 
security  rarely  attained  in  descriptive  science. 
And  the  testimony  of  the  spectroscope  is 
equally  conclusive  that  the  visible  stars, 
like  the  sun  itself,  are  made  up  almost  or 
quite  exclusively  of  the  same  chemical  ele- 
ments. Such  facts,  so  familiar  that  they  re- 
quire no  comment  or  explanation,  might 
sufficiently^  justify  the  acceptance  of  the  chem- 
ist's known  elements  as  the  only  important 
matter  in  the  universe.  But  even  more 
weighty  evidence  is  at  hand ;  I  mean  the 
so-called  periodic  classification  of  the  ele- 
ments. 

It  has  long  been  evident  that  simple  rela- 
tionships exist  in  some  cases  between  the 
atomic  weights  of  similar  elements.  For  ex- 
ample, the  atomic  weights  of  bromine,  stron- 
tium, and  selenium  are  approximately  equal 


10      THE   FITNESS  OF  THE  ENVIRONMENT 

to  the  means  of  the  atomic  weights  of  chlorine 
and  iodine,  of  calcium  and  barium,  and  of 
sulphur  and  tellurium  respectively.  More 
general  relationships  between  the  atomic 
weights  and  properties  of  the  elements  were 
first  pointed  out  by  Newlands  in  1864  and 
were  extended  by  Mendeleeff  and  Lothar 
Meyer  a  little  later.  Out  of  these  studies 
has  arisen  the  law  that  the  properties  of  the 
elements  are  periodic  functions  of  their  atomic 
weights. 

The  essential  characteristics  of  this  law  are 
best  illustrated  by  a  consideration  of  the 
relative  volumes  occupied  by  atoms  of  the 
various  elementary  substances,  the  so-called 
atomic  volumes,  which  may  be  expressed  by 
dividing  atomic  weights  by  specific  gravities. 
The  facts  are  graphically  represented  upon 
the  accompanying  diagram,  where  atomic 
weights  are  plotted  horizontally,  atomic  vol- 
umes vertically. 

Beginning  with  lithium  the  volumes  fall 
to  boron  and  carbon,  then  rise  irregularly  to 
sodium.  A  second  fall  leads  to  aluminium, 
a  second  rise  to  potassium,  and  then  the  rises 
and  '  falls  of  the  curve  are  repeated  until, 
among  the  elements  of  higher  atomic  weight, 
gaps  break  the  continuity  of  the  relationship. 
On  the  whole  curve  similar  elements  occupy 


FITNESS 


11 


-S 


s        ?        s        g 


12       THE   FITNESS  OF  THE  ENVIRONMENT 

similar  positions.  Thus  the  alkali  metals, 
lithium,  sodium,  potassium,  rubidium,  and 
caesium,  occupy  the  crests  of  the  waves;  the 
halogens,  fluorine,  chlorine,  bromine,  and 
iodine,  fall  about  midway  between  crests 
and  troughs,  and  a  little  further  study  dis- 
closes a  host  of  other  corresponding  relation- 
ships. 

Similar  periodic  variations  may  be  shown 
to  occur  in  other  physical  properties  of  the 
elements ;  —  the  melting  points,  the  boiling 
points,  the  magnetic  characteristics,  etc. 
Even  more  striking  are  the  periodic  varia- 
tions in  chemical  properties,  including  the 
general  characteristics  which  first  led  to  the 
idea  of  rational  classification,  and  more  spe- 
cific qualities  like  the  combining  powers  for 
hydrogen,  oxygen,  and  other  elements. 

The  clearest  proof  of  the  value  of  the 
periodic  classification  has  been  the  predic- 
tion of  "new"  elements,  and  accurate  fore- 
knowledge of  their  properties.  Thus  when 
Mendeleeff  first  described  the  system,  the 
element  germanium,  discovered  by  Winkler 
in  1886,  was  unknown ;  but  from  the  proper- 
ties of  the  elements  surrounding  a  gap  in  the 
system  the  Russian  chemist  was  able  to 
predict  its  properties  with  almost  incredible 
exactness,  as  the  following  table  shows. 


FITNESS 


13 


Prediction 


Observation 


Atomic  weight    .     .     . 
Specific  gravity  .     .     . 
Atomic  volume  .     .     . 
Formula  of  oxide     .     . 
Specific  gravity  of  oxide 
Formula  of  chloride     . 
Boiling  point  of  chloride 
Specific  gravity  of  chloride 
Formula  of  fluoride      .     . 
Formula  of  ethyl  compound 
Specific  gravity  of  ethyl  compound 


72.0 
5.5 
13 
GeOz 

4.7 
GeCl4 
Less  than  100' 

1.9 
GeFU 
Ge(C2H5)4 

0.96 


72.3 

5.469 
13.2 
GeOz 

4.703 
GeCl4 
86° 

1.9 
GeFL, 
Ge(C2H6)4 
Lower  than  water 


Finally  it  is  to  be  especially  noted  that, 
upon  arranging  the  known  elements  in  a 
table  rationally  constructed  upon  the  basis 
of  the  above  recorded  facts,  comparatively 
few  spaces  within  the  range  of  known  atomic 
weights  remain  to  be  filled.  The  conclusion 
is  obvious  that  very  few  elements  now  un- 
known are  possible  unless  they  possess  very 
high  atomic  weights.  But  the  apparent 
transmutation  of  radium  into  helium  is  a 
pretty  clear  indication  that  elements  of  very 
high  atomic  weight  may  be  unstable.  If 
they  have  existed  in  number  and  large  quan- 
tity, they  probably  have  long  since  ceased 
so  to  exist,  except  perhaps  in  the  interior 
of  celestial  bodies,  and  they  are  not  likely 
elsewhere  to  complicate  natural  phenomena 
by  their  unknown  properties. 


14        THE   FITNESS  OF  THE  ENVIRONMENT 


1— 1 

> 

Fe           Co            Ni 
55.9          59.0          58.7 

Ru           Rh           Pd 
101.7        103.0        106.5 

Os              Ir             Pt 

191           193.0        194.8 

> 

CL.                                                .... 

> 

^9t                        to 
o         «o     ^^    ceo                «^t- 

> 

«U5                          Ol                                        o 

-     "     ■=        fS         -.As         : 

> 

c 

12.00 

Si 

28.4 

Ti 

48.1 

Ge 

72.5 

Zr 

90.6 

Sn 
119.0 

Ce 
140.2 

Pb 
206.9 

Th 
232.5 

h-l 

K 

Be 
9.1 

Mg 
24.36 

Ca 
40.1 

Zn 
65.4 

Sr 
87.6 

Cd 
112.4 

Ba 
137.4 

Hg 
200.0 

Ra 
225 

- 

Li 
7.03 

Na 
23.05 

39.15 

Cu 
63.6 

Rb 

85.5 

Ag 
107.93 

Cs 
133 

Au 
197.2 

* 

o 

^-^i^i    :     m2    :     xS    :      :      : 

FITNESS  15 

The  behavior  of  radium  and  the  classifica- 
tion itself  suggest  one  further  idea:  the  hy- 
pothesis that  the  elements  are  genetically 
related,  that  they  have  been  evolved  by  some 
unknown  process  according  to  unknown  laws. 
Certain  it  is  that  the  properties  of  matter  are 
no  chance  phenomena,  and  that  transmuta- 
tion has  ceased  to  be  merely  a  philosopher's 
dream. 

All  of  these  familiar  facts  of  chemical  science 
fully  justify  us  in  dealing  with  matter  as  a 
known  factor  in  the  study  of  life  conditions 
in  the  universe.  For,  whatever  may  be  the 
fate  of  present  theories,  our  present  practical 
knowledge  of  the  behavior  of  matter  cannot 
fail  us  in  the  future. 

B 

ENERGY 

Contemporary  with  the  work  of  Darwin 
and  of  Mendeleeff  were  the  feats  of  Mayer, 
Joule,  Helmholtz,  Kelvin,  and  Clausius, 
whereby  ideas  of  energy  assumed  their  mod- 
ern aspect.  In  the  revolution  wrought  by 
these  men  imponderables  and  fluids  vanished 
from  this  domain,  and  energy  became  that 
which,  not  being  matter,  is  conserved.  The 
new  principles  of  the  'fifties  have  held  their 
own    until    to-day.        Meantime    they    have 


16       THE  FITNESS  OF  THE  ENVIRONMENT 

made  of  thermodynamics  (the  department  of 
science  which  is  especially  concerned  with 
the  laws  of  energy  transformation)  a  sub- 
ject which  few  who  cultivate  the  physical 
sciences  may  disregard.  Countless  develop- 
ments and  achievements  of  thermodynamics 
give  very  real  ground  for  the  belief  that  we 
may  speculate  about  the  transformations  of 
energy  in  the  universe  with  the  same  assur- 
ance that  we  have  in  discussing  chemical 
changes. 

Our  reasons  for  confidence  in  the  truth  of 
current  general  notions  of  energy,  and  in 
their  adequacy  to  account  for  any  phenomena 
so  far  as  energy  is  concerned,  wherever  life 
exists  in  the  universe,  are  manifold,  and  not 
unlike  those  which  have  been  reviewed  in  dis- 
cussing the  elements. 

Centuries  of  search  have  revealed,  in  addi- 
tion to  that  most  obvious  form  which  is 
studied  in  dynamics,  a  very  small  number  of 
varieties  or  manifestations  of  energy,  such  as 
heat,  electricity,  magnetism,  optical  energy, 
and  chemical  energy.  Such  manifestations 
of  energy  are  by  no  means  confined  to  the 
earth  or  to  the  solar  system.  Indeed  Newton 
first  worked  out  the  general  laws  of  dynamics 
and  erected  them  into  a  complete  science 
with  the  aid,  not  of  terrestrial,  but  of  astro- 


FITNESS  17 

nomical  phenomena.^  And  recent  most  re- 
markable studies  of  the  stars  have  enabled 
astronomers  to  account  for  obscure  events 
in  far  distant  parts  of  the  universe  by  the 
application  of  the  principles  of  dynamics. 
Similarly  light,  heat,  and  chemical  energy,  as 
we  know  them,  are  unquestionably  universal. 
No  doubt  the  manifestations  of  energy 
within  the  sun  and  stars,  like  the  accompany- 
ing material  phenomena  there,  can  to-day 
only  be  surmised.  For  aught  we  know, 
these  places  may,  as  has  been  guessed,  be  the 
birthplace  of  elements  and  the  seat  of  mani- 
festations   of    energy    quite    different    from 

^  "What  the  Occasion  of  Sir  Isaac  Newton's  leaving  the 
Cartesian  Philosophy,  and  of  discovering  his  amazing  Theory 
of  Gravity  was,  I  have  heard  him  long  ago,  soon  after  my  first 
Acquaintance  with  him,  which  was  1694,  thus  relate,  and  of 
which  Dr.  Pemberton  gives  the  like  Account,  and  somewhat 
more  fully,  in  the  Preface  to  his  Explication  of  his  Philos- 
ophy :  It  was  this.  An  Inclination  came  into  Sir  Isaac's 
Mind  to  try,  whether  the  same  Power  did  not  keep  the  Moon 
in  her  Orbit,  notwithstanding  her  projectile  Velocity,  which 
he  knew  always  tended  to  go  along  a  strait  Line  the  Tangent 
of  that  Orbit,  which  makes  Stones  and  all  heavy  Bodies  with 
us  fall  downward,  and  which  we  call  Gravity?  Taking  this 
Postulatum,  which  had  been  thought  of  before,  that  such 
Power  might  decrease,  in  a  duplicate  Proportion  of  the  Dis- 
tances from  the  Earth's  Center."  —  "Memoirs  of  the  Life 
of  Mr.  WiUiam  Whiston  by  Himself."  London,  1749,  Vol.  I, 
pp.  35-38.  Quoted  by  Ball.  "An  Essay  on  Newton's  Prin- 
cipia."     London,  1893,  p.  8. 


18      THE  FITNESS  OF  THE  ENVIRONMENT 

what  we  have  ever  observed.  But,  however 
interesting  and  important  such  processes  may 
be,  it  is  not  to  be  supposed  that  they  are  of 
direct  moment  in  physiological  processes. 
These  conditions  are  far  beyond  the  limits 
of  our  present  investigation.  Accordingly, 
everything  that  observation  has  taught  con- 
firms the  belief  that  energy,  like  matter,  is 
in  general  well  known  to  us.  Its  manifesta- 
tions are  few,  and  they  are  universal.  But 
just  as  the  generalizations  of  science  yield 
further  assurance  regarding  matter,  so  they 
do  not  fail  to  confirm  our  conclusions  in  the 
study  of  energy.  The  law  of  the  conserva- 
tion of  energy  and  the  law  of  the  degradation 
of  energy,  otherwise  known  as  the  first  and 
second  laws  of  thermodynamics,  clearly  in- 
dicate that  the  manifestations  of  energy  are 
not  accidental  nor  independent  of  one  an- 
other. They  are  orderly,  and  they  obey  laws. 
Energy  is  one  and  indestructible. 

Such  are  the  apparently  irrefragable  con- 
clusions of  the  brief  half  century  of  creative 
development,  from  the  time  when  Young 
first  used  the  word  "energy"  and  Bolton  and 
Watt  first  employed  the  idea  of  measuring 
energy  in  horse  power,  through  the  period  of 
Carnot's  brilliant  intuition  regarding  the  re- 
lation between  heat  and  work,  to  the  epoch 


FITNESS  19 

of  the  foundation  of  thermodynamics.^  To- 
day we  know  that  just  so  much  heat,  neither 
more  nor  less,  may  be  obtained  by  the  com- 
plete conversion  of  a  unit  of  electrical  energy 
or  by  a  given  chemical  process.  We  know, 
moreover,  that  not  every  conceivable  change 
from  one  form  of  energy  to  another  is  possible. 
On  the  whole,  energy  can  flow  in  but  one 
direction;  perpetual  motion  is  impossible; 
and  useful  energy  is  steadily  becoming  de- 
graded, dissipated,  and  useless. 

Such  laws  are  fully  worthy  of  a  place  be- 
side the  periodic  law,  and  they  justify  equal 
confidence  in  the  adequacy  of  our  current 
descriptions  of  matter  and  of  energy  for  the 
purposes  of  biology. 


SPACE  AND  TIME 

Since  Kant  revolutionized  modern  phi- 
losophy, the  whole  world  has  steadily  realized 
that  between  matter  and  energy  on  the  one 
hand,  and  space  and  time  on  the  other,  there 
is   a   real   and   highly   significant   difference.^ 

^  An  excellent  account  of  this  period  may  be  found  in 
Merz's  "History  of  European  Thought  in  the  Nineteenth 
Century,"  Vol.  II,  Chap.  VII,  "On  the  Physical  View  of 
Nature." 

2  For  a  brief  statement  of  Kant's  argument  see  Royce, 
"The  Spirit  of  Modern  Philosophy,"  pp.  121-125. 


20      THE  FITNESS  OF  THE  ENVIRONMENT 

But,  however  important  such  distinctions  may 
be  for  the  philosopher,  the  man  of  science  in 
his  practical  task  is  obliged  to  put  them 
aside  and  to  make  the  best  of  whatever  evi- 
dence experience,  observation,  and  experi- 
ment may  supply.  Out  of  such  studies  space 
and  time  have  emerged,  usefully  defined  by 
mathematical  criticism  as  substantial  parts 
of  the  edifice  of  science.^ 

There  is  no  small  difficulty  in  the  exposi- 
tion of  modern  critical  results  regarding 
space  and  time,  but  fortunately  there  is  little 
need  of  considering  them  on  the  present 
occasion.  For  in  spite  of  all  assaults  of  phi- 
losophers and  mathematicians  space  remains 
for  practical  purposes  more  certainly  than 
ever  the  Euclidian  space  of  the  ancients, 
only  it  has  become  somewhat  richer  in  char- 
acteristics. And  time  is  now  and  forever 
that  which  flows  equably,  wholly  independ- 
ent of  all  else,  though  almost  all  else  is 
dependent  upon  time.  It  is  EucKdian  space 
in  which  the  earth  moves  and  describes  its 
ellipse,  parallel  rays  of  light  never  do  meet 
in  our  practical  experience,  and  our  crystals 

^  The  works  of  Poincare,  "La  Science  et  I'Hypothese,"  "La 
Valeur  de  la  Science,"  and  "Science  et  Methode,"  published 
by  Flammarion,  may  be  consulted  for  a  popular  statement  of 
such  mathematical  studies. 


FITNESS  21 

are  in  form  the  figures  of  Euclidian  geometry. 
Our  time  flows  ever  in  proportion  to  the 
swings  of  a  pendulum,  the  propagation  of 
light,  and  the  progress  of  a  chemical  change. 
Time  and  space  are  thus  bound  to  matter 
and  energy  by  experience,  and  for  practical 
purposes  we  accept  all  four  as  science  at 
present  knows  them.^  We  cannot  doubt 
that  knowledge  of  them  will  increase  and 
ideas  of  them  change.  But  we  can  scarcely 
think  that  our  present  ideas  are  inadequate 
for  our  present  purposes,  or  that,  for  life, 
matter  will  ever  be  other  than  the  elements 
of  the  periodic  classification,  energy  that  set 
of  quantities  to  which  we  apply  the  laws  of 
thermodynamics,  and  time  and  space  the 
concepts  which  were  familiar  to  Galileo  and 
Euclid. 

IV 

THE  ORGANISM 

Thus  the  growth  of  physical  science  has 
provided  the  speculative  biologist  with  a 
very  accurate  and  extensive  description  of 
the  physico-chemical  structure  of  the  ma- 
terial universe  and  with  a  well-founded  con- 

^  In  the  present  work  we  need  have  no  concern  for  the 
so-called  principle  of  relativity. 


22       THE  FITNESS   OF  THE  ENVIRONMENT 

fidence  in  his  right  to  make  use  of  the  descrip- 
tion in  investigating  the  relationship  between 
Hfe  and  the  environment. 

The  biologist  studies  living  organisms  as 
inhabitants  of  this  world,  and  by  holding 
fast  to  physics  and  chemistry  he  has  created 
modern  physiology,  a  science  which  unites 
many,  indeed  nearly  all,  of  the  departments 
of  physics  and  chemistry  in  the  task  of  de- 
scribing the  processes  of  life. 

That  task  has  proved  an  arduous  one,  even 
in  comparison  with  the  other  enterprises  of 
science,  and  it  must  be  confessed  that  few 
of  the  departments  of  physiology  wear  an 
aspect  of  finality  which  has  long  been  famil- 
iar in  such  sciences  as  mechanics  and  crystal- 
lography, for  example.  Yet,  as  time  has 
passed,  and  the  nature  of  the  material  basis 
of  life  and  the  conspicuous  features  of  the 
mechanism  which  the  organism  presents  for 
study  have  become  more  familiar,  assurance 
has  steadily  grown  of  the  possibility  of  decid- 
ing upon  fundamental  and  essential  char- 
acteristics of  the  life  process.  No  doubt 
opinions  have  fluctuated,  and  in  different 
periods  of  the  history  of  science  particular 
phenomena  of  living  organisms  have  been 
examined,  criticized,  and  then  well-nigh  for- 
gotten. But  gradually  ideas,  ever  more  and 
more  precise,  have  arisen  and  been  accepted. 


FITNESS  23 

Until  very  recent  times,  however,  the 
main  interest  has  centered  upon  morpho- 
logical problems  and  upon  the  processes  of 
growth  and  development.  The  ancient  con- 
troversies regarding  types  and  homologous 
parts,  the  question  of  spontaneous  genera- 
tion and  the  whole  science  of  embryology, 
and  inquiries  into  the  nature  of  fermentation 
and  the  role  of  microorganisms  are  examples 
of  the  older  tendencies.  Such  interests  have, 
it  need  hardly  be  said,  lost  none  of  their  im- 
portance, but  they  scarcely  touch  the  physico- 
chemical  problem  of  the  nature  of  living 
things.  Yet  there  is  in  these  subjects  one 
point  of  view,  a  favorite  of  Cuvier's,  now, 
though  still  familiar,  less  often  emphasized, 
which  states  a  most  important  characteristic 
of  life  in  terms  of  matter  and  energy,  space 
and   time.^     Living  things  preserve,  or  tend 

^  "La  vie  est  done  un  tourbillon  plus  ou  moins  rapide, 
plus  ou  moins  complique,  dont  la  direction  est  constante, 
et  qui  entraine  toujours  des  molecules  de  memes  sortes,  mais 
ou  les  molecules  individuelles  entrent  et  d'ou  elles  sortent 
continuellement,  de  maniere  que  la  forme  du  corps  vivant 
lui  est  plus  essentielle  que  la  matiere."  ("Regne  animal," 
p.  13,  etc.)  "II  vient  sans  cesse  des  elements  du  dehors  en 
dedans :  il  s'en  echappe  du  dedans  en  dehors :  toutes  les  par- 
ties sont  dans  un  tourbillon  continuel,  qui  est  une  condition 
essentielle  du  phenomene,  et  que  nous  ne  pouvons  suspendre 
longtemps  sans  I'arreter  pour  jamais.  Les  branches  les  plus 
simples  de  I'histoire  naturelle  participent  deja  a  cette  compli- 


24       THE  FITNESS  OF  THE  ENVIRONMENT 

to  preserve,  an  ideal  form,  while  through 
them  flows  a  steady  stream  of  energy  and  mat- 
ter which  is  ever  changing,  yet  momentarily 
molded  by  life;  organized,  in  short.  This 
idea,  to  which  we  must  later  return,  could 
not  possess  in  the  early  nineteenth  century 
the  significance  and  value  which  now  attach 
to  it.  It  needed  the  explanation  which  the 
study  of  metabolism  has  at  length  provided. 

A 

METABOLISM 

Metabolism  is  the  term  applied  to  the  in- 
flow and  outflow  of  matter  and  energy  and 
their  intermediary  transformations  within  the 
organism.  Its  serious  investigation  began 
with  Lavoisier,  the  principal  founder  of  mod- 
cation  et  a  ce  mouvement  perpetuel,  qui  rendent  si  difficile 
I'application  des  sciences  generales. "  ("  Rapport,"  p.  150,  etc.) 
"  Dans  les  corps  vivans  chaque  partie  a  sa  composition  propre 
et  distincte ;  aucune  de  leurs  molecules  ne  reste  en  place ; 
toutes  entrent  et  sortent  successivement :  la  vie  est  un  tour- 
billon  continuel,  dont  la  direction,  toute  compliquee  qu'elle, 
est,  demeure  constante,  ainsi  que  I'espece  des  molecules  qui 
y  sont  entrainees,  mais  non  les  molecules  individuelles  elles- 
memes.  .  .  .  Ainsi  la  forme  de  ces  corps  leur  est  plus 
essentielle  que  leur  matiere,"  etc.  {Ibid.  p.  200.) — "  Eloges 
historiques,"  Vol.  I,  p.  200.  Quoted  by  Merz,  "A  History  of 
European  Thought  in  the  Nineteenth  Century,"  Vol.  I,  p. 
129.     Edinburgh  and  London,  1898. 


FITNESS  25 

ern  chemistry,  who  by  ingenious  experiments 
discovered  that  the  essential  feature  of  the 
chemical  process  in  the  animal  is  combus- 
tion or  oxidation,  and  that  the  amount  of  oxy- 
gen required  by  such  combustion  is  not  much 
less  than  that  needed  to  burn  substances  which 
resemble  the  foods  in  the  air.  The  problems 
which  thus  arose  have  been  studied  by  a 
host  of  later  investigators,  notably  by  Liebig 
and  Voit,  and  gradually  a  vast  array  of  facts 
concerning  the  turnover  of  matter  and  en- 
ergy in  the  body  have  been  accumulated. 
Among  other  achievements  is  the  proof  that 
the  principle  of  the  conservation  of  energy 
applies  to  the  living  organism.  These  have 
been  chemical  investigations,  carried  out  by 
chemists,  and  for  that  reason,  until  quite 
recently,  they  have  not  received  their  due 
in  general  biology. 

Meantime,  as  knowledge  of  the  balance 
sheet  of  the  body,  the  total  metabolism  so- 
called,  has  been  perfected,  more  and  more 
interest  has  developed  in  the  changes  which 
attend  the  passage  of  matter  and  energy  in 
their  various  stages  through  the  organism. 
Such  problems  at  once  demand  a  physico- 
chemical  description  of  protoplasm  as  a  nec- 
essary basis  for  their  solution.  The  same 
demand   has    also    arisen   in    other   quarters. 


26       THE   FITNESS  OF  THE  ENVIRONMENT 

Thus  the  microscope,  with  all  its  brilliant 
contributions  to  knowledge  of  the  form  and 
more  gross  structural  elements  of  the  cell, 
hardly  at  all  contributes  to  knowledge  of  its 
physico-chemical  organization  as  a  mechan- 
ism. Out  of  such  needs  a  preliminary,  if 
very  imperfect,  rational  description  of  proto- 
plasm has  arisen,  and  gradually  the  physical 
and  chemical  laws  governing  protoplasm,  its 
form,  composition,  and  stability,  its  con- 
stituent parts  and  their  mode  of  action,  and 
the  physical  and  chemical  changes  within 
it  are  being  discovered.^  The  idea  of  dur- 
able form  in  matter  and  energy  that  change 
can  now  be  applied  to  the  cell  with  greater 
advantage,  in  that  descriptions  of  the  form 
and  of  the  change  are  now  at  hand,  though 
as  yet  all  too  imperfect. 

Another  profoundly  important  contribu- 
tion of  the  science  of  metabolism  to  our 
knowledge  of  the  characteristics  of  life  is  the 
discovery  of  the  cycle  of  matter  through 
plants  and  animals.^  The  plant  takes  up 
carbonic  acid  and  water  and  a  few  other 
simple    substances    from    air    and    soil,    and 

1  This  subject  is  extensively  treated  by  Hober,  *'Physik- 
alische  Chemie  der  Zelle  und  der  Gewebe."  Leipzig,  1911, 
3ded. 

2  This  was  originally  clearly  stated  by  Lavoisier. 


FITNESS  27 

transforms  them  into  oxygen,  which  renews 
the  air,  and  sugar,  starch,  and  other  sub- 
stances, which  are  the  food  of  the  animal.^ 
These  products  the  animal  burns,  thereby 
forming  once  more  carbonic  acid  and  water, 
which  return  to  the  plant  and  so  pass  through 
the  cycle  again  and  again.  The  changes  in 
energy  which  accompany  this  process  are 
quite  different  from  the  chemical  changes. 
Starch  and  sugar  and  oxygen,  formed  in  the 
leaf  of  the  plant,  are  compounded  of  carbonic 
acid,  water,  and  sunshine.  This  sunshine, 
or  solar  energy,  wh*en  changed  into  the 
chemical  energy  of  the  carbohydrate,  is  pre- 
served and  transmitted  to  the  animal.^  In 
his  body  it  is  set  free  as  muscular  force  and 
heat,  and  then  dissipated.  Accordingly,  when 
carbonic  acid  and  water  are  combined  to 
form  sugar  and  oxygen  in  the  leaf,  it  is  al- 
ways a  new  store  of  solar  energy  which  they 
bear,  and  while  matter  goes  round  and 
round,  energy  is  being  constantly  degraded 
and  lost.  The  one  process  is  cyclic,  the 
other   moves   steadily  in   one  direction  from 

^  Our  knowledge  of  photosynthesis  is  largely  based  upon 
the  classical  work  of  N.  T.  de  Saussure,  "Recherches  Chi- 
miques  sur  la  Vegetation."     Paris,  1804. 

^  Only  after  the  establishment  of  the  principle  of  the 
conservation  of  energy  was  it  possible  to  gain  a  clear  con- 
ception of  the  energetics  of  metabolism. 


28       THE  FITNESS  OF  THE  ENVIRONMENT 

sunshine   to   the  waste   heat   of   the   animal 
body.^ 

B 

ORGANIC    CHEMISTRY 

Independent  ahke  of  general  biology  and 
of  the  science  of  metabolism  there  has  grown 
up  still  another  department  of  natural  sci- 
ence, organic  chemistry,  which  contributes 
very  materially  to  the  description  and  com- 
prehension of  living  things.  During  a  large 
part  of  the  nineteenth  century  the  efforts  of 
chemists  were  mainly  directed  to  the  cultiva- 
tion of  this  subject,  which  seeks  to  describe 
the  molecular  constitution  of  all  the  com- 
pounds of  carbon,  including  nearly  all  the 
individual  substances  which  make  up  animals 
and  plants.  Gradually,  as  organic  chemis- 
try has  progressed,  very  complete  descrip- 
tions of  the  atomic  groupings  w^ithin  the 
molecules  of  fats,^  carbohydrates,^   and   pro- 

1  Here,  as  in  so  many  other  cases,  it  is  not  the  conservation 
of  matter  and  energy,  but  the  conservation  of  matter  and  the 
degradation  of  energy  which  are  important.  For  an  exten- 
sive development  of  this  important  difference  see  B.  Brunhes, 
"La  Degradation  de  I'Energie."     Paris,  1909. 

2  Chevreul,  "Recherches  Chimiques  sur  les  Corps  Gras." 
Paris,  1823. 

^  E.  Fischer,  "  Untersuchungen  liber  Kohlenhydrate  und 
Fermente."     Berlin,  1909. 


FITNESS  29 

teins,^  the  chief  of  such  things,  and  most 
of  the  other  biologically  important  •  sub- 
stances have  been  obtained,  and  we  are  at 
length  in  possession  of  exceedingly  clear  and 
reliable  ideas  as  to  the  chemical  constitu- 
tion of  living  matter.  In  fact,  the  nature 
and  laws  of  the  chemical  composition  of  pro- 
toplasm are  actually  more  certain  than  the 
nature  and  laws  of  its  physical  structure.^ 

In  this  manner,  by  slow  degrees,  the  de- 
scription of  living  things  has  progressed,  and 
gradually  the  characteristics  of  life  have 
become  less  obscure  and  their  aspects  more 
simple.  It  cannot  be  denied  that  many 
traits  like  consciousness  and  inheritance  are, 
at  least  for  the  present,  beyond  the  scope  of 
description  in  terms  of  matter  and  energy, 
and  the  fundamental  riddle  shares  this  de- 
tachment.3     But   the   physico-chemical   basis 

^  E.  Fischer,  "  Untersuchungen  iiber  Aminosauren,  Poly- 
peptide und  Proteine."     Berlin,  1906. 

^  Substantial  progress  in  the  latter  field  is  nearly  all  of 
very  recent  date,  almost  wholly  since  the  sudden  rise  of 
physical  chemistry. 

^  "But  now,  having  confessed  that  Life  as  a  principle  of 
activity  is  unknown  and  unknowable  —  that  while  its  phe- 
nomena are  accessible  to  thought  the  implied  noumenon  is 
inaccessible  —  that  only  the  manifestations  come  within  the 
range  of  our  intelligence  while  that  which  is  manifested  lies 
beyond  it;  we  may  resume  the  conclusions  reached  in  the 
preceding  chapters.     Our  surface  knowledge  continues  to  be 


30        THE  FITNESS  OF  THE  ENVIRONMENT 

of  life  is  firmly  established  in  the  world  of  our 
senses.  On  the  whole  the  composition  of 
living  matter,  its  ph^^sical  structure,  the 
changes  of  matter  and  energy  which  consti- 
tute the  metabolic  process,  together  with  the 
totality  of  such  changes,  which  make  up  the 
fundamental  economic  process  of  that  largest 
community  which  consists  of  all  living  beings, 
are  all  clearly  defined. 

C 

THE   CHARACTERISTICS  OF  LIFE 

Under  the  circumstances  it  is  certainly  no 
rash  enterprise  to  seek  a  definition  of  some 
of   the   essential   characteristics   of   life.     Al- 

a  knowledge  of  its  kind,  after  recognizing  the  truth  that  it  is 
only  a  surface  knowledge. 

"For  the  conclusions  we  lately  reached  and  the  definition 
emerging  from  them,  concern  the  order  existing  among  the 
actions  which  living  things  exhibit ;  and  this  order  remains  the 
same  whether  we  know  or  do  not  know  the  nature  of  that 
from  which  the  actions  originate.  We  found  a  distinguish- 
ing trait  of  Life  to  be  that  its  changes  display  a  correspond- 
ence with  coexistences  and  sequences  in  the  environment; 
and  this  remains  a  distinguishing  trait,  though  the  thing 
which  changes  remains  inscrutable.  The  statement  that 
the  continuous  adjustment  of  internal  relations  to  external 
relations  constitute  Life  as  cognizable  by  us,  is  not  invali- 
dated by  the  admission  that  the  reality  in  which  these  rela- 
tions inhere  is  incognizable."  —  Herbert  Spencer,  "The 
Principles  of  Biology."  New  York  and  London,  1909,  Vol. 
I.    Revised  and  enlarged  edition,  pp.  122-123. 


FITNESS  31 

though  it  is  probably  far  beyond  our  present 
power  to  make  a  complete  study  of  the  prob- 
lem, I  feel  sure  that  a  brief  analysis  will 
justify  certain  very  definite  conclusions.  Life 
as  we  know  it  is  a  physico-chemical  mechan- 
ism, and  it  is  probably  inconceivable  that  it 
should  be  otherwise.^  As  such,  it  possesses, 
and,  we  may  well  conclude,  must  ever  pos- 
sess, a  high  degree  of  complexity,  —  physi- 
cally, chemically,  and  physiologically;  that  is 
to  say,  structurally  and  functionally.  We 
cannot  imagine  life  which  is  no  more  complex 
than  a  sphere,  or  salt,  or  the  fall  of  rain,  and, 
as  we  know  it,  it  is  in  fact  a  very  great  deal 
more  complex  than  such  simple  things.  Next, 
living  things,  still  more  the  community  of 
living  things,  are  durable.  But  complexity 
and  durability  of  mechanism  are  only  pos- 
sible if  internal  and  external  conditions  are 
stable.  Hence,  automatic  regulations  of  the 
environment  and  the  possibility  of  regulation 
of  conditions  within  the  organism  are  essen- 
tial to  life.  It  is  not  possible  to  specify  a 
large  number  of  conditions  which  must  be 
regulated,  but  certain  it  is  from  our  present 
experience  that  at  least  rough  regulation  of 

^  I  mean,  of  course,  for  the  purposes  of  physical  and  chem- 
ical study.  With  such  qualifications  the  statement  is  prob- 
ably no  longer  open  to  objection  from  any  quarter. 


32        THE  FITNESS  OF  THE  ENVIRONMENT 

temperature,  pressure,  and  chemical  consti- 
tution of  environment  and  organism  are 
really  essential  to  life,  and  that  there  is  great 
advantage  in  many  other  regulations  and  in 
finer  regulations.  Finally,  a  living  being  must 
be  active,  hence  its  metabolism  must  be 
fed  with  matter  and  energy,  and  accordingly 
there  must  always  be  exchange  of  matter 
and  energy  with  the  environment. 

Returning  to  the  concept  of  the  organism 
as  a  durable  form  through  which  flow  matter 
and  energy,  it  is  now  possible  to  make  these 
ideas  more  vivid.  The  complex  structure  of 
the  living  being  is  relatively  stable,  alike  in 
the  chemical  composition  of  its  individual 
constituent  molecules,  in  their  proportions 
and  amounts,  in  their  aggregation  into  the 
invisible  structural  elements  of  protoplasm, 
in  the  visible  parts  of  the  cell,  in  the  organs 
and  tissues,  and  finally  in  toto,  as  a  man  or  a 
tree.  Similarly  stable  are  the  physical  con- 
ditions within  this  structure:  temperature, 
pressure,  alkalinity,  and  osmotic  pressure. 
Finally,  that  which  surrounds  it,  the  imme- 
diate environment,  possesses  also  a  high  de- 
gree of  stability,  or  if  the  organism  be  very 
complex,  it  may  be  that  it  has  an  eflScient  pro- 
tection against  change  of  environment;  a  skin 
which  insulates,  for  instance.    But  in  this  case 


FITNESS  S3 

it  has  also  acquired  an  environment,  a  milieu 
interieur  for  its  cells,  —  like  the  blood  and 
lymph,  —  which  serves  the  same  purpose  as 
stability  of  the  external  environment,  and  ex- 
ercises the  further  function  of  supplying  food. 

It  is  through  this  structure,  in  the  process 
of  metabolism,  that  matter  and  energy  flow. 
Entering  in  various  forms  and  quantities, 
they  are  temporarily  shaped  exactly  to  the 
form  and  condition  of  the  organism;  they 
conform  to  the  characteristics  of  the  king- 
dom, class,  order,  family,  genus,  species,  and 
variety  to  which  it  belongs,  and  they  assume 
even  the  characteristics  of  the  individual 
itself.^  Then  they  depart  through  the  va- 
rious channels  of  excretion. 

When  these  ideas  are  reduced  to  their  very 
simplest  forms,  it  appears  that  life  must  be 
highly  complex  in  structure  and  function; 
that  the  conditions  of  the  environment  must 
be  regulated,  and  that  there  must  be  very  exact 
regulation  of  conditions,  both  structural  and 
functional  within  the  organism,  and  finally, 
that,  while  life  is  active,  there  must  be  ex- 
change of  both  matter  and  energy  with  the 
environment.  Complexity,  regulation,  and 
food  are  essential  to  life  as  we  know  it,  and 

^  Science  is,  of  course,  still  at  a  loss  for  an  adequate  gen- 
eral explanation  of  such  processes. 


34      THE  FITNESS  OF  THE  ENVIRONMENT 

in  truth  we  cannot  otherwise  conceive  of  life, 
or  indeed  of  any  other  durable  mechanism. 
For  my  part  I  do  not  doubt  that  these  pos- 
tulates are  quite  as  true  of  the  world  of  our 
senses  as  are  the  fundamental  laws  of  matter 
and  energy,  space  and  time. 

Obviously  these  few  conclusions  can  make 
no  claim  to  completeness.  Fully  to  describe 
life,  the  discovery  of  many  other  fundamen- 
tal characteristics  is  necessary,  including  such 
as  are  related  to  inheritance,  variation,  evo- 
lution, consciousness,  and  a  host  of  other 
things.  But  in  the  formation  and  logical 
development  of  such  ideas  there  is  danger 
of  fallacy  at  every  step,  and  since  the  present 
list  will  suffice  for  the  present  purpose,  further 
considerations  of  this  sort  are  best  dispensed 
with.  This  subject  should  not  be  put  aside, 
however,  w^ithout  clear  emphasis  that  the 
postulates  which  have  been  adopted  above 
are  extremely  meager.  The  only  motives  for 
abandoning  further  search  are  the  economy 
and  the  security  which  are  thus  insured,  and 
the  very  great  difficulty  of  extending  the 
list.  Any  one  who  is  familiar  with  similar 
efforts  to  elucidate  the  essential  character- 
istics of  life,  such  as  that  of  Wallace,^  cannot, 
I  fear,  fail  to  perceive  the  extreme  limitations 

^A.  R.  Wallace,  "Man's  Place  in  the   Universe,"     New 


FITNESS  35 

which  are  imposed  upon  inquiry  by  assuming 
complexity,  regulation,  and  metabolism  ex- 
clusively. Perhaps  in  reality  these  postu- 
lates are  only  two.  Metabolism  might  with- 
out difficulty  be  included  under  regulation, 
but  the  consideration  of  such  purely  logical 
questions  is  beside  the  present  purpose. 
However,  these  are  probably  the  character- 
istics of  the  organism  which  are  best  fitted  for 
discussion  in  relation  to  the  physico-chemical 
phenomena  of  matter  and  energy,  and  it  is 
barely  possible  that  no  others  bear  the  same 
simple  relations  to  the  outside  world. 

York,  1903,  Chaps.  X  and  XI,  especially  the  following 
statement :  — 

"The  physical  conditions  on  the  surface  of  our  earth 
which  appear  to  be  necessary  for  the  development  and  main- 
tenance of  living  organisms  may  be  dealt  with  under  the  fol- 
lowing headings :  — 

"  1.  Regularity  of  heat  supply,  resulting  in  a  limited  range 
of  temperature. 

"2.  A  sufficient  amount  of  solar  light  and  heat. 

"  3.  Water  in  great  abundance,  and  universally  distributed. 

"4.  An  atmosphere  of  sufficient  density,  and  consisting  of 
the  gases  which  are  essential  for  vegetable  and  animal  life. 
These  are  Oxygen,  Carbonic-acid  gas,  Aqueous  vapor,  Ni- 
trogen, and  Ammonia.  These  must  all  be  present  in  suitable 
proportions. 

"5.  Alternations  of  day  and  night." 

It  must  be  remembered,  however,  that  such  conclusions 
depend  upon  reasoning  from  analogy,  a  dangerous  proceed- 
ing. 


36      THE  FITNESS  OF  THE  ENVIRONMENT 


THE  PROBLEM 

We  may  now  return  to  the  problem  of  the 
fitness  of  the  environment.  So  long  as  ideas 
of  the  nature  of  living  things  remain  vague 
and  ill-defined,  it  is  clearly  impossible,  as  a 
rule,  to  distinguish  between  an  adaptation  of 
the  organism  to  the  environment  and  a  case 
of  fitness  of  the  environment  for  life,  in  the 
very  most  general  sense.  No  doubt  there 
are  clear  instances  of  both  phenomena  which 
require  no  close  analysis  for  their  interpreta- 
tion. Thus  the  hand  is  surely  an  instance 
of  adaptation,  and  the  anomalous  expansion 
of  water  on  cooling  near  its  freezing  point 
an  instance  of  environmental  fitness.  But 
how  much  weight  is  to  be  assigned  to  adapta- 
tion and  how  much  to  fitness  in  discussing  the 
relations  between  marine  organisms  and  the 
ocean  .f^  Evidently  to  answer  such  questions 
we  must  possess  clear  and  precise  ideas  and 
definitions  of  living  things.  Life  must  by  ar- 
bitrary process  of  logic  be  changed  from  the 
varying  thing  which  it  is  into  an  independ- 
ent variable  or  an  invariant,  shorn  of  many 
of  its  most  interesting  qualities  to  be  sure, 
but  no   longer   inviting  fallacy   through   our 


FITNESS  37 

inability    to    perceive    clearly    the    questions 
involved. 

Such  is  the  purpose,  and  the  justification, 
for  setting  up  the  postulates  of  complexity, 
regulation,  and  metabolism  as  inherent  in 
that  mechanism  which  is  called  the  living 
organism.  With  them,  at  length,  we  face 
the  problem  which  awaits  us.  To  what  ex- 
tent do  the  characteristics  of  matter  and 
energy  and  the  cosmic  processes  favor  the 
existence  of  mechanisms  which  must  be  com- 
plex, highly  regulated,  and  provided  with 
suitable  matter  and  energy  as  food  ?  If  it  shall 
appear  that  the  fitness  of  the  environment  to 
fulfill  these  demands  of  life  is  great,  we  may 
then  ask  whether  it  is  so  great  that  we  can- 
not reasonably  assume  it  to  be  accidental, 
and  finally  we  may  inquire  what  manner 
of  law  is  capable  of  explaining  such  fitness  of 
the  very  nature  of  things. 


CHAPTER  II 
THE  ENVIRONMENT 

I 

ASTRONOMY 

AN  examination  of  the  relationship  be- 
tween Hfe  and  the  environment,  in  which 
by  means  of  the  simpHfying  postulates  pre- 
viously developed  life  is  arbitrarily  taken  as 
an  invariant,  should,  if  it  is  to  be  quite  general, 
rest  upon  a  physico-chemical  description  of 
the  whole  universe.  We  require  to  know  the 
form  and  structure  of  stars  and  of  interstellar 
space,  of  nebulae  and  of  solar  systems,  and 
the  conditions  and  changes  which  accompany 
such  aggregations  of  matter.  Evidently  this 
requirement  can  be  but  imperfectly  fulfilled, 
and  yet  one  need  not  be  too  apologetic  in 
venturing  the  attempt.  In  the  end,  to  be 
sure,  we  shall  found  our  argument  upon  the 
safe  basis  of  terrestrial  phenomena,  but  mean- 
time it  will  be  an  advantage  to  consider  con- 
ditions far  and  wide. 

38 


THE  ENVIRONMENT  39 

The  science  of  cosmography  is  probably 
the  earhest  of  all  the  natural  sciences,  and 
cosmological  speculation  appears  to  accom- 
pany it  from  the  outset.  Long  before  the 
dawn  of  history  the  Chaldeans  possessed 
much  accurate  information  about  the  stars, 
and  the  zodiac  was  known  to  the  Egyptians 
not  less  than  fifteen  centuries  before  our  era. 
Always  pursued  with  great  interest,  such  studies 
received  their  first  provisional  systematic  for- 
mulation at  the  hands  of  Hipparchus  in  the 
second  century  B.C.  He,  the  greatest  of  the 
astronomers  of  antiquity,  succeeded  in  bring- 
ing the  apparent  movements  of  the  sun,  moon, 
and  planets  into  an  arbitrary  scheme  which 
was  nearly  perfect  for  the  sun,  though  less 
so  for  the  other  movable  celestial  bodies.  He 
also  measured  and  catalogued  the  positions 
of  a  large  number  of  fixed  stars.  Upon  this 
secure  foundation  of  quantitative  observa- 
tions modern  astronomy  has  built.  At  the 
beginning  of  the  modern  period  Copernicus, 
Tycho  Brahe,  Kepler,  Galileo,  and  Newton 
reduced  the  phenomena  of  the  solar  system 
to  law.  At  a  later  day  speculations  based 
upon  their  results  and  upon  growing  knowl- 
edge of  physics  and  chemistry  led  Thomas 
Wright,  Kant,  and  finally  Laplace  to  a  ra- 
tional, if   somewhat   imperfect,   cosmological 


40      THE  FITNESS  OF  THE  ENVIRONMENT 

theory  of  the  solar  system.  Finally,  ever 
more  accurate  observations  and  the  marvel- 
ous fertility  of  spectroscopical  investigations 
have  brought  the  stars  within  our  reach. 

The  whole  universe  now  appears  to  be  not 
unlike  our  part  of  it,  both  chemically  and 
physically.  The  same  forms  of  matter,  the 
same  material  aggregates,  the  same  manifes- 
tations of  energy,  and  similar  movements  are 
everywhere  present.  The  stars  are  no  longer 
changeless,  but  violently  active  bodies  ;  they 
are  no  longer  permanent,  but  evolving  sys- 
tems; they  are  born,  they  grow,  age,  and 
die;  and  throughout  their  evolution  they 
obey  laws,  which,  though  as  yet  imperfectly 
known,  appear  to  be  common  to  all.  Mean- 
time the  study  of  nebulae,  comets,  and  meteor- 
ites has  kept  pace  with  other  departments  of 
the  science,  and  our  interpretation  of  the  re- 
sults of  stellar  astronomy  ^  constantly  gains 
from  ever  increasing  knowledge  of  the  physical 
and  chemical  processes  in  the  sun. 

The  universe  which  thus  gradually  has  been 
revealed  to  the  astronomer  is  made  up  of  a 
relatively  small  number  of  types  of  material 

^  A  description  of  such  facts  from  the  physico-chemical 
point  of  view  may  be  found  in  Arrhenius's  "Lehrbuch  der 
kosmichen  Physik."  Leipzig,  1903.  A  brief  popular  account 
of  some  of  the  facts  in  the  same  author's  "Worlds  in  the  Mak- 
ing," translated  by  Boms.     New  York  and  London,  1908. 


THE  ENVIRONMENT  41 

aggregation.  These  include  luminous  dense 
bodies  like  the  sun  and  stars;  non-luminous 
dense  bodies  like  the  earth,  the  moon,  the 
planets,  and  invisible  partners  of  certain  stars ; 
nebulae,  comets,  and  meteorites.  The  larger 
of  these  bodies  are  separated  by  vast  extents 
of  space  which  contain  only  rare  meteorites, 
perhaps  minute  traces  of  gaseous  material, 
and  cosmic  dust.  There  can  be  little  doubt 
that  other  types  of  bodies  do  not  commonly 
occur  in  that  portion  of  the  universe  which  is 
open  to  astronomical  investigation.  Both  the 
enormous  collections  of  astronomical  data 
which  are  now  at  hand  and  the  beginnings 
of  clear  knowledge  of  cosmic  processes  justify 
this  belief.  Of  what  may  lie  beyond  the 
visible  stars  we  can,  of  course,  know  nothing. 

The  nature  of  the  stars  is  revealed  to  us 
chiefly  by  study  of  their  spectra,  according 
to  which  they  have  been  roughly  classified, 
by  Vogel  ^  for  example,  quite  simply  into 
three  principal  types. 

I.  White  stars  in  which  there  is  marked 
evidence  of  the  presence  of  hydrogen,  or,  in 
some  instances,  helium.  The  stars  of  this 
class  undoubtedly  are  extremely  hot,  the 
helium  stars  probably  especially  so.  Their 
atmospheres  seem  to  be  very  dense    and  to 

^  See  Arrhenius's  "Lehrbuch,"  pp.  23-27. 


42        THE  FITNESS  OF  THE  ENVIRONMENT 

consist  of  hydrogen  or  helium  or  a  mixture 
of  the  two  gases.  There  is  evidence  that  some 
of  these  stars  possess  very  high  rotational 
velocities. 

II.  Yellow  stars,  including  the  sun,  whose 
spectra  indicate  the  presence  of  hydrogen  and 
numerous  metals,  —  sodium,  iron,  calcium, 
magnesium,  etc.  The  lines  which  show  the 
presence  of  hydrogen  in  the  stars  of  this  type 
vary  in  intensity.  The  current  belief  is  that 
those  stars  which  appear  to  possess  more 
hydrogen  are  the  hottest.  The  stars  of  this 
type  are  less  hot  than  those  of  type  I. 

III.  Reddish  stars  whose  spectra  show  little 
or  no  sign  of  the  presence  of  hydrogen,  but 
indicate  that  of  chemical  compounds,  in- 
cluding hydrocarbons.  The  presence  in  these 
spectra  of  the  lines  of  sodium,  iron,  calcium, 
and  magnesium  is  clearly  established.  Stars 
of  this  type  are  evidently  the  coolest  of  lumi- 
nous dense  bodies. 

This  classification  is,  of  course,  provisional 
and  unsatisfactory,  and  probably  sometimes 
results  in  bringing  together  relatively  unlike 
stars  and  in  separating  such  as  are  very  much 
akin.  Moreover,  subdivisions  in  the  classifica- 
tion are  necessary  and  hard  to  make.  Other 
better  but  more  complex  classifications  appear 
to  exist,  but  they  suffer  only  in  less   degree 


THE  ENVIRONMENT  43 

from  like  defects.  In  short  all  the  known 
facts  can  best  be  explained  by  the  assump- 
tion that  the  stars  represent  different  stages 
of  development  of  suns.^     In  that  case  this 

^  "Bei  Durchmusterung  der  Specktra  der  verschiedenen 
Sterne  kann  man  sich  nicht  des  Gedankens  erwehren,  dass 
die  verschiedenen  Sterngruppen  verschiedenen  Entwick- 
lungsstadien  entsprechen.  Die  jiingsten  und  warmsten 
aller  Sterne  waren  (nach  der  allgemeinen  Ansicht,  vgl.  weiter 
unten  Kap.  Kosmogonie)  diejenigen  der  ersten  Gruppe. 
Das  kontinuierhche  Licht,  welches  von  dem  eigenthchen 
Stemkorper  ausstrahlt,  rlihrt  haupstachhch  von  Kondensa- 
tionen,  wolkenartigen  Bildungen  in  der  Atmosphare  der 
Sterne,  zum  geringeren  Teil  von  den  stark  verdichteten 
Metalldampfen  im  Inneren  des  Sterns  her.  In  den  hoheren 
Schichten  dieser  Atmosphare  finden  sich  die  leichten  Gase, 
Wasserstoff  oder  Hehum  oder  alle  beide,  weiter  unten  Metall- 
dampfe.  Bei  den  Sternen  erster  Klasse  ist  die  Atmosphare 
der  leichten  Gase  so  dick  und  heiss,  dass  die  fiir  uns  sicht- 
baren  Kondensationen  beinahe  alle  in  diesen  oberen  Schichten 
vor  sich  gehen,  Wir  sehen  deshalb  keine  oder  nur  schwache 
Metalllinien,  dagegen  sehr  starke  Wasserstoff-  oder  Helium- 
linien.  Bisweilen  ist  die  Menge  und  Temperatur  der  leichten 
Gase  genligend,  um  helle  Umkehrungen  dieser  Linien  zu 
verursachen.  Bei  dem  zweiten  Spektralt;s'pus  ist  die  Ab- 
klihlung  weiter  fortgeschritten,  so  dass  Kondensationen 
nicht  nur  in  den  hochsten  Schichten  der  Atmosphare,  sondem 
auch  innerhalb  der  Metallatmosphare  vorkommen.  Man 
sieht  dann  die  dunklen  Metalllinien  scharf  hervortreten.  Das 
Zuriicktreten  des  violetten  Endes  des  Spektrums  und  einige 
schwache  Bander  im  roten  Teil  deuten  auf  niedrigere  Tem- 
peratur hin.  Bei  den  rotlichen  Sternen  treten  tiefe  Temper- 
atur andeutende  Erscheinungen  noch  mehr  hervor.  Die  bei 
denselben  gewohnlich  vorkommende  Veranderlichtkeit  lasst 
auf  das  Vorkommen  von  kalteren  und  warmeren  Perioden 


44        THE   FITNESS  OF  THE  ENVIRONMENT 

development  or  evolution  must  be  a  contin- 
uous process  through  which  every  sun  slowly 
passes,  and  on  the  whole  all  suns  must  be 
much  alike.  Certainly  we  have  the  best  of 
evidence  to  justify  the  assumption  that  most 
stars,  including  the  sun,  have  very  much  the 
same  chemical  composition,  and  that  differ- 
ences in  spectra  are  due  to  the  slowly  progress- 
ing physico-chemical  changes  which  have 
accompanied  the  process  of  cooling. 

Needless  to  say,  the  chemical  composition 
of  the  sun  itself  is  far  better  known  than  that 
of  the  stars.  Particularly  prominent  among 
his  constituent  elements  are  those  above 
mentioned:    hydrogen,  sodium,  calcium,  mag- 

schliessen,  wie  solche  in  geringerem  Maasstab  bei  unserer 
Sonne  durch  die  Fleekenperiode  sieh  kundgeben.  Zuletzt 
wird  die  Leuchtkraft  der  Sterne  sehr  schwach  und  das  Licht 
ausgepragtrot,  der  relativ  niedrigen  Temperatur  entsprech- 
end.  Nach  diesem  Stadium  kommt  dasjenige,  worin  die 
dunklen  ultraroten  Strahlen  allein  herrschen,  der  Stern  ist  in 
einen  nichtleuchtenenden  Himmelskorper  Ubergegangen  (vgl. 
weiter  unten  Kap.  Kosmogonie) . 

Im  Grossen  und  Ganzen  zeigen  die  Sterne  dieselbe  chemi- 
sche  zusammensetzung  wie  die  Sonne.  Die  hervorragende 
Rolle  des  Wasserstoffs  und  Heliums,  sowei  des  Eisens,  Na- 
triums, Calciums  und  Magnesiums,  macht  sieh  iiberall  be- 
merkbar.  Es  ist  dann  kein  Zweifel,  dass  unsere  Sonne  mit 
den  Fixsternen  sehr  nahe  verwandt  ist,  und  zwar  ist  sie  als 
ein  Fixstern  der  ersten  Abteilung  in  der  zweiten  Klasse  an- 
zusehen."  —  Arrhenius,  "Kosmische  Physik."  Leipzig, 
1903,  p.  27. 


THE  ENVIRONMENT  45 

nesium,  and  iron.  Also  some  others,  which 
because  of  their  low  density  are  concentrated 
near  the  surface,  are  known  to  occur.  The 
elements  which  have  not  yet  been  discovered 
are  those  like  the  metalloids  which  do  not  un- 
der ordinary  circumstances  give  well-marked 
spectra,  and  those  like  gold,  platinum,  and 
mercury,  whose  higher  specific  gravities  may 
be  supposed  to  cause  their  accumulation  in 
the  interior.  Carbon  is  certainly  present, 
and  almost  certainly  oxygen  as  well.  Indeed 
it  is  only  reasonable  to  conclude,  as  Kirchhoff 
originally    suggested,^    that   all    the   elements 

^  **  Diese  Vorstellung  von  der  Beschaffenheit  der  Sonne 
stimmt  mit  der  von  Laplace  begriindeten  Hypothese  liber 
die  Bildung  unseres  Planetensystems  uberein.  Wenn  die 
Masse,  die  jetzt  in  den  einzelnen  Korpern  dieses  Systems 
verdichtet  ist,  in  fruheren  Zeiten  einen  zusammenhangenden 
Nebel  von  ungeheurer  Ausdehnung  bildete,  durch  dessen 
Zusammenziehung  Sonne,  Planeten  und  Monde  entstanden 
sind,  so  mussten  alle  diese  Korper  bei  ihrer  Bildung  im 
wesentlichen  von  ahnlicher  chemischer  Zusammensetzung 
sein.  Die  Geologie  hat  gelehrt,  dass  die  Erde  einst  in  glii- 
hend  flussigem  Zustande  sich  befunden  hat ;  man  muss  anneh- 
men,  dass  auch  die  anderen  Korper  unseres  Systems  einmal 
in  einem  solchen  gewesen  sind.  Die  Abkiihlung,  die  infolge 
der  Ausstrahlung  der  Warme  bei  alien  eingetreten  ist,  hat 
aber  bei  ihnen  sehr  verschiedene  grade  erlangt ;  und  wahrend 
der  Mond  kalter  als  die  Erdegeworden  ist,  ist  die  Temperatur 
des  Sonnenkorpers  noch  nicht  unter  die  Weissgliihhitze 
gesunken.  Die  irdische  Atmosphare,  die  jetzt  nur  wenige 
Elemente  enthalt,  musste,  als  die  Erde  noch  gliihte,  eine  viel 
mannigfaltigere  Zusammensetzung  haben ;    alle  in  der  Gliih- 


46        THE  FITNESS  OF  THE  ENVIRONMENT 

are  present  in  the  sun,  and  very  often,  at 
least,  in  the  stars.  Exceptions  may  arise,  but 
probably  they  will  hardly  suffice  to  invalidate 
the  rule. 

The  large,  dark,  dense  bodies  which  are 
directly  known  to  us  are  the  planets  and 
their  satellites.  There  are,  however,  many  in- 
dications that  the  heavens  are  occupied  by 
great  numbers  of  *'dead"  suns,  incrusted  and 
therefore  no  longer  luminous.  Such  appear 
to  be  the  only  conclusions  which  can  be  drawn 
from  a  study  of  the  energetics  of  solar  evolu- 
tion, for  sooner  or  later  a  sun  must  cool  from 
loss  of  energy  until  at  length  a  crust  forms,  and, 
barring  catastrophe,  it  must  then  endure  for- 
ever. Moreover,  as  we  have  seen,  the  varying 
aspects  of  the  stars  seem  to  disclose  suns  in 
all  stages  of  such  a  process. 

More  nearly  direct  is  the  evidence  furnished 
by  study  of  variable  stars  of  the  Algol  type. 
Algol  itself  (y8  Persei)  is  a  star  of  second 
magnitude  with  a  period  of  2  days,  20  hours, 
48  minutes,  53.8  seconds.     During  each  period 

hitze  fliichtigen  Stoffe  mussten  in  ihr  vorkommen.  Eine 
entsprechende  Beschaffenheit  muss  heute  noch  die  Atmosphare 
der  Sonne  besitzen."  —  G.  Kirchhoff,  —  "  Untersuchungen 
Uber  das  Sonnenspektrum  und  die  Spektren  der  Chemisehen 
Elemente."  Abhandlungen  der  Koniglichen  Akademie  der 
Wissenschaften  zu  Berlin,  1861.  Zweite,  durch  einen  An- 
hang  vermehrte  Ausgabe.     Berlin,  1862. 


THE  ENVIRONMENT  47 

for  about  2|^  days  it  shines  with  constant  in- 
tensity; thereupon  it  begins  to  dechne  and  in 
approximately  4j  hours  sinks  to  its  minimum 
of  brightness;  then  it  becomes  gradually 
brighter  until  after  4^  hours  more  it  has  re- 
attained  its  full  brilliancy.  This  behavior  is 
explained  by  the  supposition  that  Algol  is 
accompanied  by  a  dark  star  and  that  their 
movements  are  such  that  a  partial  eclipse 
occurs  every  69  hours.  Pickering  has  suc- 
ceeded in  calculating,  upon  the  assumption 
that  the  dark  star  as  a  whole  intercepts  the 
rays  of  Algol,  the  approximate  sizes,  veloci- 
ties, and  orbits  of  these  two  stars,  one  of 
which  is  quite  invisible.  Many  similar  phe- 
nomena lead  to  similar  conclusions  regarding 
other  variable  stars. 

It  is  apparent  that  such  dark  bodies,  whether 
extinct  suns  or  planets,  represent  another 
stage  in  celestial  evolution.  Their  past  his- 
tories may  be  various,  for  there  is  still  room 
for  much  doubt  as  to  the  manner  of  formation 
and  origin  of  planets,  but  at  any  rate  all  are 
probably  derived  from  luminous  stars  or 
planets  through  the  process  of  cooling,  with 
its  accompanying  crust  formation.  Like  their 
earlier  forms,  they  must  therefore  be  made  up 
of  matter  as  we  know  it,  since  when  a  heavenly 
body  puts  on  a  crust,  it  does  not  change  the 


48        THE  FITNESS  OF  THE  ENVIRONMENT 

matter  of  which  it  is  composed.  Finally 
terrestrial  chemistry  completes  the  evidence 
regarding  the  composition  of  such  astronom- 
ical bodies ;  geophysics  that  regarding  their 
state.  The  number  of  extinct  suns  is  prob- 
ably very  great ;  Arrhenius  thinks  it  not  un- 
likely that  they  may  be  one  hundred  times 
more  numerous  than  the  luminous  stars. ^ 

It  is  more  difficult  to  gain  a  clear  idea  of 
the  nebulae,  for  such  aggregations  of  matter 
are  very  diverse  in  appearance,  and  none  lie 
near  enough  to  the  earth  for  us  to  study  them 
as  we  study  the  solar  system.  However,  in- 
vestigation of  new  stars,  of  the  spiral  forms  of 
many  nebulae,  of  the  so-called  star  rifts 
which  appear  to  be  due  to  the  movement  of  a 
large  body  through  a  nebula,  sweeping  up 
smaller  bodies  and  leaving  a  channel  behind, 
and  a  variety  of  considerations  dependent 
upon  the  modern  development  of  the  sciences 
of  physics  and  chemistry,  all  contribute  to  a 
growing  belief  that  nebulae  may  often,  and 
sometimes  at  least  do  certainly  arise  from  col- 
lisions between  dense  bodies.  Further,  the 
nature  of  the  processes  by  which  stars  may  be 
formed  out  of  nebulae  becomes  constantly 
better  understood,  and  while  there  is  small 
ground  to  regard  our  present  science  of  nebulae 

1"  Worlds  in  the  Making,"  p.  151. 


THE  ENVIRONMENT  49 

as  final,  there  is  none  at  all  for  the  belief 
that  anything  essentially  inexplicable  either 
physico-chemieally  or  genetically  will  be  dis- 
covered in  their  organization. 

Putting  aside  all  contentious  matters,  it  is 
abundantly  clear  that  nebulae,  however  they 
may  vary  among  themselves,  are  made  up  of 
vast  extents  of  gaseous  material  and  dust 
which  are  exceedingly  rare  and  at  very  low 
temperature,  and  that  they  may  contain  all 
kinds  of  foci  of  condensation,  from  stars  to 
meteorites,  in  great  variety  of  forms  and 
conditions. 

On  the  whole  the  common-sense  judgment 
that  the  solar  system  may  be  taken  as  a  fair 
sample  of  the  universe,  and  that  its  probable 
evolution  is  in  the  main  typical  of  cosmic 
evolution  in  general  seems  to  be  well  founded. 
Any  other  hypothesis  does  violence  to  a  host 
of  facts,  and  to  the  larger  generalizations  of 
modern  science. 

II 

POSSIBLE    ENVIRONMENTS 

If  now  we  seek  to  make  the  best  of  existing 
astronomical  knowledge,  as  hastily  sketched, 
in  the  study  of  our  biological  problem,  cer- 
tain considerations  at  once  present  themselves^ 


50       THE  FITNESS  OF  THE  ENVIRONMENT 

Obviously  it  is  not  everywhere  in  such  a  uni- 
verse that  hfe  can  exist.  The  visible  stars, 
like  the  sun,  certainly  cannot  support  life. 
Throughout  such  bodies  durable  and  complex 
arrangements  of  matter  are  impossible,  for  if 
formed,  they  must  be  at  once  dissipated  by 
catastrophes  far  greater  than  any  which  can 
occur  upon  the  earth's  crust.  The  enormous 
intensity  of  heat,  even  in  the  most  superficial 
parts  of  suns,  must  effectually  preclude  any 
state  of  matter  but  the  gaseous,  and  thus 
prevent  the  existence  there  of  anything  of 
the  nature  of  a  mechanism.  Such  bodies, 
apart  only  from  continuous  variation  from 
center  to  periphery,  in  the  proportions  of  the 
elements,  in  density,  and  in  the  nature  of  the 
chemical  unions  between  the  elements,  must  be 
essentially  homogeneous.  They  can  scarcely 
possess  relatively  as  much  structure  as  the 
earth's  atmosphere.  In  truth  the  sun  itself 
seems  to  be  the  one  and  only  durable  solar 
mechanism. 

Not  less  evident  is  the  impossibility  of  active 
life  in  interstellar  space  or  in  nebulae.  Dor- 
mant life  (panspermia)  may  indeed  be  possible 
universally,  except  only  in  the  neighborhood 
of  suns.  But  if  life  is  to  be  fed,  if  there  is  to 
be  active  metabolism,  including  exchange  of 
matter  with  the  environment,  something  more 


THE   ENVIRONMENT  51 

nourishing  than  the  rare  molecules  of  a  nebula, 
or  the  still  rarer  particles  of  interstellar  space, 
must  be  provided. 

We  may  safely  conclude,  therefore,  on  the 
basis  of  our  reliable  knowledge  of  the  universe, 
that  active  life  can  exist  probably  only  upon 
a  dense,  crusted  body  ^;  for,  of  course,  the  in- 
terior of  the  earth  is  no  better  suited  to  life 
than  is  the  interior  of  the  sun. 

We  have  perhaps  taken  a  long  road  to  arrive 
at  so  familiar  an  idea.  But  our  task  involves 
the  consideration  of  every  conceivable  form 
of  life,  not  merely  that  relatively  anthropo- 
morphic kind  which  we  commonly  think 
of  when  speculating  loosely  regarding  life  in 
other  worlds. 

It  is  indeed  possible  that  the  common-sense 
judgment  of  the  universe  which  declares  our 
solar  system  to  be  on  the  whole,  in  its  funda- 
mental characteristics,  typical  of  every  such 
system  ma^^  turn  out  to  be  in  some  respects 
unjustified.  For  the  present,  however,  so 
long  as  we  use  it  only  as  an  indication  of  the 
direction  in  which  we  are  to  turn  our  atten- 
tion, there  is  certainly  no  risk  whatever  in  fol- 
lowing this  hypothesis  in  the  later  discussion. 

^  For  an  interesting  discussion  of  the  necessary  conditions 
of  existence  see  P.  Lowell,  "Mars  as  the  Abode  of  Life." 
The  Macmillan  Company,  New  York,  1908. 


52       THE  FITNESS  OF  THE  ENVIRONMENT 

III 

GEOPHYSICS 

Let  us,  accordingly,  now  examine  such 
phenomena  as  are  Hkely  to  occur  upon  the 
surfaces  of  bodies  which  in  the  course  of 
cosmic  evolution  have  acquired  a  solid  crust. 
In  faithfully  carrying  out  such  a  plan,  the 
sciences  of  geology  and  meteorology  must  be 
brought  under  contribution,  and  climatic 
conditions  must  receive  especial  attention. 
Not,  to  be  sure,  that  our  globe  in  every  respect 
can  fairly  be  taken  as  meteorologically  typical 
of  all  incrusted  bodies.  On  the  contrary,  there 
are  a  large  number  of  phenomena  which  are 
unquestionably  of  highest  significance  in  fa- 
voring the  existence  of  life  on  this  particular 
planet  which  appear  to  be  accidental  and  prob- 
ably   somewhat    uncommon.^     Such    are   the 

^  These  also  have  been  favorite  subjects  in  the  works  on 
natural  theology.  The  Bridgewater  Treatises  of  Whewell 
and  of  Prout  are  replete  with  illustrations,  those  of  Whewell 
often  moderately  expounded,  while  Front's  are,  as  a  rule,  most 
curious  and  antiquated. 

"Lastly,  who  will  venture  to  assert  that  the  distribution 
of  sea  and  of  land,  as  they  now  exist,  though  apparently  so 
disproportionate,  is  not  actually  necessary  as  the  world  is 
at  present  constituted.^  What  would  be  the  result,  for 
instance,  if  the  Pacific  or  the  Atlantic  oceans  were  to  be  con- 
verted into  continents  ?     Would  not  the  climates  of  the  exist- 


THE  ENVIRONMENT  53 

size  of  the  sun  taken  in  relation  with  its  dis- 
tance from  the  earth ;  the  size  of  the  earth, 
which  enables  it  to  retain  its  present  atmos- 
phere ;  the  eccentricity  of  its  orbit  and  the 
inclination  of  the  ecliptic ;  the  relative 
amounts  of  land  and  sea,  and  a  host  of  other 
factors.  Together  these  probably  make  of 
the  earth,  in  comparison  with  other  bodies, 
an  extremely  favorable  abode  for  the  living 
organism.  Yet  it  cannot  be  denied  that  in 
detailed  chemical  constitution  the  earth  is 
certainly  more  or  less  typical  of  all  similar 
bodies.  Moreover  the  earth's  crust  and  its 
atmosphere,  being  formed  in  accordance  with 

ing  continents,  as  formerly  observed,  be  completely  changed 
by  such  an  addition  to  the  land,  and  the  whole  of  their  fertile 
regions  be  reduced  to  arid  deserts  ?  Now,  this  distribution 
of  sea  and  of  land,  so  wonderfully  adapted  as  it  appears  to 
be  to  the  present  state  of  things,  depends  of  course  in  a  great 
measure  upon  the  absolute  quantity  of  water  in  the  world. 
While,  on  the  other  hand,  the  relative  gravity  of  water,  as  com- 
pared with  that  of  the  earth,  keeps  the  ocean  within  its 
destined  limits,  notwithstanding  its  incessant  motion.  Thus 
Laplace  has  shown  that  the  world  would  have  been  con- 
stantly liable  to  have  been  deluged  from  the  slightest  causes, 
had  the  mean  density  of  the  ocean  exceeded  that  of  the  earth  ! 
Hence  the  adjustment  of  the  quantity  of  water  and  of  its 
density,  as  compared  with  that  of  the  earth,  afford  some  of 
the  most  marked  and  beautiful  instances  of  design."  —  Prout, 
The  Bridgewater  Treatises,  Treatise  VIH,  "Chemistry, 
Meteorology,  and  the  Function  of  Digestion."  London,  1834, 
pp.  186-187. 


54       THE  FITNESS  OF  THE  ENVIRONMENT 

general  laws,   are  likewise   typical   or   at    all 
events  were  so  at  the  time  of  their  origin. 

Neither  can  the  change  in  crust  and  atmos- 
phere which  time  has  wrought  be  wholly 
unique,  though  here  a  possible  exception  may 
again  arise  in  the  action  of  life  itself.  Since 
we  do  not  at  present  positively  know  of  the 
existence  of  life  elsewhere  and  certainly  have 
no  detailed  knowledge  of  its  nature,  we  can- 
not feel  sure  that  the  conversion  of  atmos- 
pheric carbonic  acid  into  oxygen  and  coal  is 
either  a  universal  or  a  common  occurrence. 
In  details  of  the  geological  process  indeed  there 
may  well  be  marked  differences.  Probably  the 
greatest  variation  will  occur  in  the  relative 
duration  of  conditions  like  those  which  we 
now  enjoy  on  the  earth,  the  length  or  brevity 
of  the  period  from  the  full  establishment  of 
the  circulation  of  water  by  evaporation,  cloud 
formation,  rainfall,  with  the  flow  of  lakes  and 
streams,  until  its  extinction  by  cold.  Thus 
there  is  more  liability  of  error  in  an  analyis 
of  the  general  characteristics  of  those  spon- 
taneous changes  which  must  occur  upon  the 
surface  of  a  body  after  the  formation  of  a 
crust  than  there  is  in  the  attempt  to  dis- 
cover the  general  characteristics  of  stellar 
evolution.  But  here  again  our  knowledge  is 
not  based  upon  terrestrial  phenomena  alone. 


THE  ENVIRONMENT  55 

With  greater  or  less  completeness  and  accu- 
racy the  atmospheres  of  the  moon,  of  Mars, 
and  of  other  planets  have  been  studied  and 
accounted  for. 

IV 

THE    ATMOSPHERE 

Even  at  the  earliest  period  in  the  evolu- 
tion of  a  typical  star  there  appears  to  be 
a  progressive  variation  in  chemical  composi- 
tion from  center  to  periphery.  Theoreti- 
cally it  seems  inevitable  that  the  heaviest 
elements  should  be  concentrated  in  the  interior 
and  that  those  of  lowest  atomic  weight  should 
be  present  in  greatest  amount  near  the  sur- 
face. Actually,  as  above  stated,  spectro- 
scopic investigation  fully  confirms  this  view. 
Thus  the  spectra  of  typical  hot  stars  show 
that  hydrogen  is  an  invariable  constituent 
of  their  superficial  parts.  Indeed  the  uni- 
versal presence  of  hydrogen  under  such  cir- 
cumstances is  undoubtedly  one  of  the  most 
clearly  established  facts  of  stellar  astronomy. 
As  stars  cool  and  become  red  the  spectral 
changes  quite  as  unmistakably  point  to  the 
presence  of  carbon.  Accordingly  we  possess 
the  best  of  evidence  and  the  best  of  reasons 
for   the   belief   that   large    quantities   of   hy- 


56       THE  FITNESS  OF  THE  ENVIRONMENT 

drogen  and  carbon  must  exist  at  or  near 
the  surface  when  a  crust  forms  upon  a  cool- 
ing star. 

The  nature  of  the  chemical  combinations 
into  which  these  elements  at  first  enter  is 
perhaps  open  to  some  question.  But  as  the 
temperature  falls  in  the  cooling  of  a  sun  or 
planet  the  affinities  of  carbon  and  hydrogen 
for  oxygen  increase,  so  that  carbonic  acid  and 
water  must  normally  result.  For  oxygen 
is  almost  certainly  present  in  the  sun;  it  is 
found  in  meteorites,  and  the  vast  store  of  it 
in  the  earth's  atmosphere  and  crust  (roughly 
one  half  of  their  total  mass)  justifies  the  be- 
lief that  it  is  everywhere  one  of  the  commonest 
of  elements.  Hence  an  atmosphere  contain- 
ing water  and  carbonic  acid  appears  to  be  a 
normal  envelope  of  a  new  crust  upon  a  cooling 
body.  Even  were  not  these  substances  at 
first  present  in  such  an  atmosphere,  volcanoes 
must  soon  belch  them  forth  in  enormous 
quantities  to  relieve  the  pressure  which  inevi- 
table chemical  processes  set  up. 

It  is  clear  that  no  one  can  give  an  exhaus- 
tive description  of  the  formation  of  the  earth's 
atmosphere  and  the  changes  which  underlie 
vulcanism,  so  long  as  the  theoretical  considera- 
tions involved  remain  often  more  obscure  than 
the  facts.     However,  be  the  process  what  it 


THE  ENVIRONMENT  57 

may,  it  is  at  least  automatic,  and  must  repeat 
itself  in  other  similar  circumstances. 

There  is,  moreover,  direct  evidence  in  sup- 
port of  the  above  conclusions.  Spectro- 
scopic investigation  has  proved  the  presence 
of  water  vapor  in  the  atmospheres  of  Mars, 
Venus,  Jupiter,  and  Saturn,  and  nobody  has 
suggested  what  the  snowcaps  of  Mars  may  be 
unless  they  are  real  snow  (hoarfrost)  or,  im- 
probably, carbonic  acid.  Lowell  and  Arrhe- 
nius  agree  in  considering  them  snowcaps.^ 

In  the  earth's  atmosphere  carbonic  acid  has 
been  very  largely  converted  into  oxygen  and 
vegetable  matter,  which  later  has  been  turned 
into  enormous  quantities  of  coal.  It  is,  in 
fact,  possible,  in  accordance  with  the  sugges- 
tion of  Koene,  that  all  the  oxygen  of  the 
atmosphere  has  been  thus  formed  from  car- 
bon dioxide,  and  that  therefore  coal,  peat,  and 
other  similar  substances  within  the  earth  are 
chemically  equivalent  to  the  oxygen  now  free. 

If  a  typical  atmosphere  must  contain  water 
and  carbon  dioxide,  its  evolution  must  ob- 
viously be  in  part  conditioned  by  the  presence 
of  these  substances.  Hence  terrestrial  meteor- 
ology, no  less  than  terrestrial  geology,  must  be 
in  greater  or  less  degree  a  special  case  of  a 

1  Arrhenius,  "Kosmische  Physik,"  p.  173;  Lowell,  "  Mars 
as  the  Abode  of  Life,"  p.  81. 


58      THE   FITNESS  OF  THE  ENVIRONMENT 

general  process,  and  meteorological  condi- 
tions on  the  earth  cannot  be  perfectly 
unique. 

A  number  of  circumstances,  however,  cause 
far  greater  variations  in  meteorological  pro- 
cesses than  in  most  other  phenomena  which 
have  yet  been  discussed.  For  instance,  on 
small  astronomical  bodies  with  weak  gravi- 
tational attractions  atmospheres  cannot  long 
endure.  Like  the  moon  these  bodies  must 
gradually  lose  nearly  all  their  gases  to  space. 
Such  loss  has  almost  certainly  occurred  from 
the  earth  itself,  and  probably  accounts  for 
the  absence  of  hydrogen  and  helium  from  the 
air.  These  gases,  being  very  light,  are  not 
attracted  with  sufficient  force  to  the  earth, 
and  gradually  rise  to  the  upper  level  of  the 
atmosphere  and  fly  away.  Again,  in  the  ab- 
sence of  a  near-by  sun  which  steadily  provides 
energy  to  balance  loss  by  radiation,  the  period 
during  which  water  and  carbonic  acid  can 
remain  in  an  atmosphere  must  be  relatively 
short.  Gradually,  but  in  a  time  wholly  in- 
considerable in  comparison  with  the  duration 
of  the  terrestrial  atmosphere,  the  gases  sur- 
rounding bodies  so  placed  must  condense  and 
then  solidify.  Finally,  a  body  which  con- 
stantly turns  one  face  to  a  sun  must  slowly 
condense  its  whole  atmosphere  upon  its  dark, 


THE  ENVIRONMENT  59 

cold  surface,  and  so  no  less  certainly  be  de- 
prived of  a  gaseous  envelope  and  of  oceans. 

Accordingly  it  appears  safe  to  say  that 
really  durable  atmospheric  conditions  depend 
upon  sufficient  size  of  the  planet,  the  presence 
of  a  sun,  and  rotation.^  No  doubt  a  host  of 
other  factors  which  exist  in  the  case  of  the 
earth  are  only  less  important.  In  any  event, 
all  such  phenomena,  though  varied  by  chance, 
are  of  automatic  origin,  and  whatever  may  be 
the  peculiarities  of  our  solar  system  there  is 
no  reason  to  suppose  that  like  conditions 
are  not  of  frequent  occurrence.  Throughout 
space  there  must  be  thousands  of  planets 
which,  like  the  earth  and  Mars,  are  enveloped 
in  an  atmosphere  that  endures  through  count- 
less centuries,  and  that  contains  great  quan- 
tities of  water  and  carbon  dioxide. 

All  such  atmospheres  must  in  greater  or 
less  degree  manifest  general  meteorological 
phenomena.  There  must  be  winds  and  clouds, 
rain  and  snow  and  ice,  the  formation  of  oceans 
and  ocean  currents,  streams  and  lakes,  all  in- 
terrelated by  complex  cyclic  processes  which 
endure.  Tides,  too,  and  magnetic  and  elec- 
trical   phenomena    cannot    be    absent,    while 

^  A  full  discussion  of  all  such  problems  will  be  found  in  the 
"Lehrbuch"  of  Arrhenius  and  in  S.  Gunther's  "Handbuch 
der  Geophysik."     Two  volumes,  Stuttgart,  1897-1898. 


60      IHE  FITNESS  OF  THE  ENVIRONMENT 

the  action  of  water  through  long  ages  must 
accompHsh  its  gigantic  work  of  disintegration 
and  sedimentation.  Soil  must  be  formed,  and 
water  must  penetrate  it.  In  short  a  possible 
abode  of  life  not  unlike  the  earth  apparently 
must  be  a  frequent  occurrence  in  space. 


GENERAL  COSMOGRAPHICAL  CONCLUSIONS 

Such,  in  the  present  state  of  knowledge, 
are  the  general  cosmographical  views  which 
naturally  suggest  themselves  to  one  who 
considers  the  possibility  of  life  throughout 
the  universe.  The  solar  system  appears  to 
be,  in  its  most  general  traits,  a  fair  sample 
of  the  whole;  the  sun  is  a  typical  star;  the 
planets  are  certainly  members  of  a  large  class 
of  similar  bodies.  These  various  types  of 
material  aggregation  are  a  good  deal  alike 
wherever  they  occur.  They  are  formed  of 
the  same  matter,  probably  in  very  much  the 
same  proportions.  They  are  actuated  by  the 
same  manifestations  of  the  same  energy,  and 
their  evolutionary  histories  are  similar.  One 
and  all  are  likely  to  possess,  for  a  longer  or 
shorter  time,  climates  which  make  life  possible. 
On  the  other  hand,  it  is  already  obvious  that 


THE  ENVIRONMENT  61 

the  solar  system,  and  especially  the  earth 
among  planets,  are  very  favorable  for  life, 
partly  through  apparently  accidental  circum- 
stances. Putting  aside,  therefore,  the  biological 
fitness  of  the  special  climates  of  the  earth  both  as 
a  familiar  fact,  and  as  possibly  in  no  small  de- 
gree accidental,  we  may  more  advantageously 
give  our  attention  at  once  to  other  phenomena 
which  appear  to  be  of  a  far  more  general 
character,  —  the  occurrence  of  large  quanti- 
ties of  water  and  carbon  dioxide  in  the  atmos- 
phere, and  the  fundamental  meteorological 
processes  which  their  presence  involves.  Ni- 
trogen and  various  other  substances  auto- 
matically find  a  place  beside  water  and  car- 
bonic acid,  but  it  will  be  convenient  to  pass 
them  by  or  to  postpone  the  consideration 
until  other  aspects  of  the  subject  have  been 
more  fully  developed. 


VI 


,    THE  PRIMARY  CONSTITUENTS  OF  THE 
ENVIRONMENT 

Of  course  a  consideration  of  the  prop- 
erties of  water  and  carbonic  acid  might 
be  approached  from  a  study  of  terrestrial 
processes  exclusively.  But  since  the  assump- 
tion that  such  phenomena  are  common  occur- 


62       THE   FITNESS  OF  THE  ENVIRONMENT 

rences  throughout  the  universe,  and  that  they 
are  the  normal  result  of  cosmic  evolution,  does 
not  in  any  way  modify  the  subsequent  course 
of  the  inquiry,  there  appears  to  be  no  loss  of 
logical  security  from  its  introduction.  Mean- 
while the  evidence  that  the  special  phenomena 
under  discussion  are  probably  the  nowise  ex- 
ceptional outcome  of  the  operation  of  general 
laws,  and  not  merely  sporadic,  cannot  fail  to 
lend  weight  to  whatever  conclusions  may 
ultimately  be  reached. 

Obviously  it  is  in  the  physical  and  chemical 
attributes  of  these  two  compounds  and  their 
constituent  elements  that  we  find  very  many 
of  the  conditions  which  make  life  possible 
upon  the  earth.  They  are  material,  provided 
and  mobilized  automatically,  out  of  which 
living  things  undoubtedly  can  be  formed. 
Moreover  if  we  limit  our  study  to  the  physico- 
chemical  properties  of  water  and  carbonic 
acid,  and  to  the  compounds  of  carbon,  hydro- 
gen, and  oxygen,  we  shall  greatly  simplify  our 
problem.  It  cannot  be  denied  that  this  re- 
striction, no  less  than  the  earlier  decision  to 
restrict  the  postulated  characteristics  of  life 
to  complexity,  regulation,  and  metabolism,  is 
sure  to  limit  the  inquiry,  often  perhaps  in  a 
very  unwelcome  manner.  On  the  other  hand, 
the   gain   in   economy   and   security   is   once 


THE  ENVIRONMENT  63 

more  of  great  importance,  and  at  present  is 
perhaps  essential  to  clear  thinking.  Such  a 
procedure  manifestly  influences  not  at  all  the 
validity  of  any  conclusions  which  may  be 
reached ;  only  it  must  not  be  forgotten  that 
the  conclusions  apply  directly  to  our  limited 
field  of  inquiry  alone. 

VII 

THE  ULTIMATE  PROBLEM 

Such  is  the  outcome  of  a  preliminary 
glance  at  the  many  departments  of  science 
which  are  necessarily  involved  in  the  ques- 
tion of  fitness  of  the  environment.  Living 
things  permit  themselves  to  be  simplified  into 
mechanisms  which  are  complex,  regulated, 
and  provided  with  a  metabolism ;  the  environ- 
ment, by  a  series  of  eliminations,  is  reduced 
to  water  and  carbonic  acid.  These  are  sim- 
plifications counseled  solely  by  expediency. 
Neither  logical  process  is  necessary ;  each  in- 
volves a  disregard  for  many  circumstances 
which  might  be  of  weight  in  the  present  in- 
quiry. But  in  the  end  there  stands  out  a 
perfectly  simple  problem  which  is  undoubt- 
edly soluble.  That  problem  may  be  stated 
as  follows :  In  what  degree  are  the  physical, 
chemical,    and    general    meteorological    char- 


64       THE  FITNESS  OF  THE  ENVIRONMENT 

acteristics  of  water  and  carbon  dioxide  and 
of  the  compounds  of  carbon,  hydrogen,  and 
oxygen  favorable  to  a  mechanism  which  must 
be  physically,  chemically,  and  physiologi- 
cally complex,  which  must  be  itself  well  regu- 
lated in  a  well-regulated  environment,  and 
which  must  carry  on  an  active  exchange  of 
matter  and  energy  with  that  environment  ? 

The  first  step  in  seeking  a  solution  must  be 
to  review  the  data  of  physics  and  chemistry 
which  describe  the  properties  of  water  and 
carbonic  acid,  having  due  regard  to  their 
meteorological  significance.  Such  data  of  the 
highest  accuracy  exist  in  great  profusion,  for 
almost  every  conceivable  property  of  these 
substances  has  been  studied  with  patient  care. 
Next,  the  properties  of  the  compounds  of 
carbon,  hydrogen,  and  oxygen  must  be  con- 
sidered, and  some  of  the  characteristics  of 
the  chemical  reactions  into  which  they  enter 
must  be  discussed.  For  this  examination  the 
unparalleled  development  of  the  science  of 
organic  chemistry  provides  ample  material. 
All  of  these  things  must  be  scrutinized  quan- 
titatively as  well  as  qualitatively,  and  here 
again  there  is  no  lack  of  necessary  information. 

Immediately  one  advantage  of  the  method 
here  proposed  becomes  evident.  We  can  deal 
with    the    familiar    abstractions    of    physical 


THE  ENVIRONMENT  65 

science,  —  specific  heat,  coeflficient  of  expan- 
sion, solubility,  heat  of  reaction,  etc.,  —  and 
thereby  we  shall  gain  all  the  advantages  of 
the  most  exact  sciences.  No  qualifications, 
no  doubtful  or  contentious  matter,  no  imper- 
fect descriptions  need  enter. 

In  this  manner  it  will  be  easy  to  estimate 
the  absolute  biological  fitness  in  certain  re- 
spects of  water  and  carbonic  acid,  and  at  once 
a  host  of  automatic  results  of  their  proper- 
ties will  become  evident.  Many  of  these  re- 
sults, such  as  the  nearly  constant  temperature 
of  the  ocean,  the  ample  rainfall,  the  freezing 
of  water  upon  the  surface,  the  great  variety  of 
carbon  compounds,  are  familiar  subjects  of 
speculation,  though  since  Darwin  little  in- 
terest has  been  manifested  in  them ;  others, 
only  recently  brought  to  light  by  the  growth 
of  physical  science,  are  nearly  or  quite  un- 
known in  this  connection.  All  deserve  to 
receive  more  serious  attention  from  biologists 
than  is  at  present  vouchsafed  them,  for  they 
constitute  a  part  of  the  very  foundation  of 
general  biology,  and  they  cause  many  of  the 
phenomena  with  which  man  is  concerned  in 
his  struggle  for  mastery  of  the  environment. 

Yet  the  mere  exposition  of  such  facts  and 
relationships  cannot  suffice  in  a  discussion  of 
the  fitness  of  the  environment.     In  the  first 


66      THE  FITNESS  OF  THE  ENVIRONMENT 

place  these  are  in  the  main  famihar  ideas, 
and  if  they  were  altogether  conclusive  to 
prove  the  existence  of  really  significant  fitness, 
if  they  could  be  regarded  as  alone  adequate 
to  establish  the  necessity  of  putting  fitness  by 
the  side  of  adaptation  as  a  coordinate  factor 
in  causing  the  marvels  of  life,  it  is  hard  to  be- 
lieve that  they  would  have  been  so  long  neg- 
lected. In  the  second  place  there  is  nothing 
comparative  about  such  information.  Water 
is  indeed  a  wonderful  substance  which  fills 
its  place  in  nature  most  satisfactorily,  but 
would  not  another  substance  do  as  well  ?  Is 
not  ammonia,  for  example,  a  possible  substi- 
tute ?  And  are  there  not  many  other  chemical 
bodies  which  might,  in  a  very  different  world, 
serve  equally  useful  purposes  ?  Perhaps,  too, 
the  great  variety  of  carbon  compounds  which 
are  known  to  the  chemist  are  known  only  be- 
cause the  vital  processes  furnish  an  abundance 
of  material  with  which  to  experiment.  Is  it 
not  possible,  therefore,  that  another  element, 
silicon,  for  instance,  may  enter  into  even 
greater  varieties  of  compounds  ?  It  is  such 
questions,  ever  present  in  the  minds  of  men  of 
science,  yet  never  carefully  scrutinized  to  see 
if  an  answer  be  possible,  which,  I  suspect,  have 
long  deflected  attention  from  this  subject. 
Clearly,  therefore,  it  will  be  necessary  to 


THE   ENVIRONMENT  67 

compare  the  properties  of  water  and  carbonic 
acid  and  of  the  carbon  compounds  with  those  of 
other  substances.  It  will  be  necessary  to  find 
out  whether  these  substances  are  not  only  fit 
but  fittest,  —  and  this  no  doubt  is  a  task  of  a 
very  different  sort.  It  may  even  seem  at  first 
sight  an  impossible  one,  but  I  hope  to  show 
that  this  is  not  the  case,  and  that  in  spite 
of  the  incompleteness  of  our  physical  and 
chemical  knowledge,  it  may  be  pressed  to  a 
satisfactory  issue.  A  few  remarks  may  now 
indicate  the  general  line  of  thought  we  shall 
pursue,  and  then  the  actual  study  must  pro- 
vide the  proof. 

VIII 

THE  METHOD  OF  SOLUTION 

The  very  constant  temperature  of  the  ocean 
is  a  most  important  factor  in  the  economy  of 
nature.  It  constitutes,  for  example,  a  vital 
regulation  of  the  environment  of  a  large  pro- 
portion of  all  the  living  organisms  of  the  world, 
and  it  has  many  other  important  "functions." 
This  constancy  of  temperature  is  in  large  part 
due  to  the  magnitude  of  the  specific  heat  of 
water.  Other  things  being  equal,  the  greater 
the  specific  heat  of  water,  the  more  constant 
must  be  the  temperature  of  the  ocean.     If, 


68      THE   FITNESS  OF  THE  ENVIRONMENT 

then,  the  specific  heat  of  water,  as  is  actually 
the  case,  be  nearly  or  quite  a  maximum  among 
all  specific  heats,  it  follows  that  the  fitness  of 
water  in  this  respect  is  nearly  maximal. 

Again  the  ocean  contains  an  astonishing 
variety  of  substances  in  solution,  and  they 
are  present  often  in  large  quantities.  In  this 
manner  a  very  great  supply  of  food  in  very 
great  variety  is  offered  marine  organisms. 
Of  course  such  richness  of  the  environment  is 
an  exceedingly  favorable  circumstance  for  the 
organism,  and  it  is  due  principally  to  the 
ability  of  water  to  dissolve  a  multitude  of 
things  in  large  quantities.  It  is  not  to  be 
supposed  that  the  substances  present  in  sea 
water  are  all  of  use  to  every  organism.  This 
need  not  be  the  case  at  all ;  but  a  variety  of 
supplies  which  may  be  adapted  to  special  re- 
quirements as  they  arise,  here  iodine,  there  cop- 
per, for  instance,  is  a  very  genuine  advantage. 
Further,  the  vast  utility  of  the  solvent  action 
of  water  in  blood,  lymph,  and  all  the  body 
fluids  is  too  patent  to  call  for  comment.  If, 
now,  it  can  be  shown  that  the  eflSciency  of 
water  is  nearly  or  quite  a  maximum,  as  it 
really  is,  among  all  known  solvents,  then  it 
must  be  evident  that  in  another  respect  the 
fitness  of  water  is  nearly  or  quite  maximal. 

Again   the   amount   of   energy   that   is   re- 


THE  ENVIRONMENT  69 

quired  to  tear  apart  molecules  of  water,  and 
to  liberate  hydrogen  and  oxygen,  is  very  great 
indeed,  and  when  hydrogen  and  oxygen  re- 
combine  to  form  water,  this  energy  must 
reappear,  —  under  ordinary  circumstances  as 
heat.  This  fact,  too,  is  very  favorable  for  the 
organism,  because  almost  all  compounds  which 
contain  hydrogen  yield  a  great  deal  of  energy 
when  they  are  burned ;  they  are,  in  short,  great 
reservoirs  of  energy  which  can  be  tapped  in 
the  process  of  metabolism.  If,  therefore,  the 
heat  of  combustion  of  hydrogen  be  nearly  or 
quite  a  maximum,  as  it  is,  among  all  sub- 
stances, it  is  clear  that  water  is  again,  in  an- 
other respect,  most  wonderfully  fitted  for  life. 

Finally,  if  it  be  true,  and  such  is  the  case, 
that  very  few  of  the  substances  which  share 
the  fitness  of  water  in  one  of  these  character- 
istics also  share  or  approach  its  fitness  in 
either  of  the  others,  and  that  none  possesses 
all  these  qualifications  in  a  degree  that  merits 
consideration,  it  must,  I  conceive,  be  admitted 
that  so  far  as  the  investigation  has  proceeded 
water  is  the  only  possible  fit  substance. 

A  criticism  may  here  be  made ;  are  there 
not  other  substances  which  possess  other 
groups  of  qualifications  which  water  lacks  ? 
And  that  is  a  difficulty  which  is  even  harder 
to  meet.     But  in  the  first  place  it  is  evident 


70      THE   FITNESS  OF  THE  ENVIRONMENT 

that  there  are  not  an  infinity  of  important 
physical  properties ;  in  fact  there  are  very 
few.  And  in  the  second  place  it  is  evident, 
both  from  centuries  of  experience  in  physical 
science  and  from  the  postulates  above  adopted 
regarding  life,  which  undoubtedly  do  in  the 
main  describe  its  physico-chemical  character- 
istics, that  very  few  properties  indeed  are  of 
importance  in  the  least  comparable  with  those 
which  I   have   mentioned. 

Finally,  it  is  in  the  highest  degree  probable 
that  we  are  acquainted  with  most  of  the  truly 
essential  physical  properties,  and  know  them  as 
biologically  important,  when  they  are  so  ;  and  I 
think  we  shall  find  it  possible  to  consider  them 
all,  and  thus  to  make  the  argument  complete. 

Meanwhile  it  should  be  noted  that  there  are 
two  different  ways  of  illustrating  the  fitness 
of  a  physical  property.  Properly  employed, 
both  are  free  from  fallacy,  and  it  will  be  de- 
sirable for  us  to  employ  both.  Thus  it  may 
be  shown,  as  in  the  case  of  the  temperature  of 
the  ocean,  that  a  particular  property  of  water, 
its  high  specific  heat,  automatically  produces 
a  maximum  of  something  which  is  favorable 
to  life.  Or  again,  as  in  the  case  of  the  regula- 
tion of  the  temperature  of  the  human  body  by 
the  process  of  perspiration,  it  may  be  shown 
that  a  particular  property  of  water,  its  high 


THE  ENVIRONMENT  71 

heat  of  vaporization,  has  been  utiHzed  through 
adaptation  of  the  organism  to  secure  very 
high  efhciency  in  a  physiological  process. 

Such  is  the  method  which  must  be  followed 
in  order  to  decide  the  question  of  the  fitness  of 
the  environment.  The  physico-chemical  char- 
acteristics of  water,  carbonic  acid,  and  the 
carbon  compounds  are  to  be  taken  up  one  by 
one,  and  their  absolute  and  relative  magnitudes 
considered.  The  possible  utility  of  such  proper- 
ties, both  automatically  and  through  process  of 
organic  adaptation,  must  then  be  estimated, 
bearing  in  mind  the  fundamental  characteris- 
tics of  the  living  organism  which  have  been 
arbitrarily  postulated.  Finally  the  various 
favorable  qualities  of  water,  carbonic  acid, 
and  the  carbon  compounds  must  be  grouped 
together  in  order  to  see  if  they  constitute  a 
unique  ensemble  of  fitness,  among  all  possible 
chemical  substances,  for  a  living  organism 
which  must  be  complex,  regulated,  and  en- 
gaged  in    active   metabolism. 

At  length  the  problem  of  fitness  appears  in 
a  simple  form.  The  road  to  a  solution  is 
open,  and  we  may  now  proceed  to  an  untram- 
meled  discussion  of  unexceptionable  data  and 
well-known  laws  of  physics,  chemistry,  meteor- 
ology, and  physiology.  Without  further  hypo- 
thetical difficulties,  these  must  lead  to  the  goal. 


CHAPTER  III 
WATER 

GENERAL  CONSIDERATIONS 

IT  was  assuredly  not  chance  that  led  Thales 
to  found  philosophy  and  science  with  the 
assertion  that  water  is  the  origin  of  all  things. 
Whether  his  belief  was  most  influenced  by 
the  wetness  of  animal  tissues  and  fluids,  or  by 
early  poetic  cosmogonies,  or  by  the  ever  pres- 
ent importance  of  the  sea  to  the  lonians,^ 
however  vague  his  conception  of  water  may, 
indeed  must,  have  been,  he  at  least  expressed 
a  conclusion  which  proceeded  from  experience 
and  serious  reflection.  Later,  when  positive 
knowledge  had  already  grown  to  be  a  sub- 
stantial basis  for  speculation,  both  meteor- 
ological and  chemical  views  contributed  to 
the  decision  of  Empedocles  and  Aristotle  to 
include  water  among  the  elements.^  And  it 
is  especially  worthy  of  note  that  of  earth,  air, 

1  Windelband,    "Handbuch    der    Altertumswissenschaft," 
V.  1.  139.     Nordlingen,  1888. 

2  Windelband,  I.e.;   S.  GUnther,  "  Geschichte   der  Natur- 
wissenschaften."     Reclam,  Leipzig,  Vol.  I,  p. 19. 

72 


WATER  73 

fire,  and  water  the  last  is  the  only  one  which 
happens  to  be  an  individual  chemical  com- 
pound. From  that  day  to  this  the  unique 
position  of  water  has  never  been  shaken.  It 
remains  the  most  familiar  and  the  most  im- 
portant  of   all    things. 

Within  a  comparatively  recent  time,  to  be 
sure,  it  has  definitely  lost  its  claim  to  be  a  true 
element,  in  the  modern  sense,  but  meanwhile 
almost  every  great  development  of  science  has 
but  contributed  to  make  its  importance  more 
clear.  In  physics,  in  chemistry,  in  geology, 
in  meteorology,  and  in  biology  nothing  else 
threatens  its  preeminence.  The  physicist  has 
perforce  chosen  it  to  define  his  standards  of 
density,  of  heat  capacity,  etc.,  and  as  a  means 
to  obtain  fixed  points  in  thermometry.  The 
chemist  has  often  been  almost  exclusively 
concerned  with  reactions  which  take  place  in 
aqueous  solution,  and  the  unique  chemical 
properties  of  water  are  of  fundamental  sig- 
nificance in  most  of  the  departments  of  his 
science.  In  geology  neptunism  has  at  length 
won  a  certain  though  incomplete  truimph  over 
plutonism,  and  the  action  of  water  now  appears 
to  be  far  the  most  momentous  factor  in  geolog- 
ical evolution.^     The  meteorologist  perceives 

/  ^  "Of  all  geological  agencies  water  is  the  most  obvious  and  i^ 
apparently  the  greatest,  though  its  eflBciency  is  conditioned 


74      THE  FITNESS  OF  THE  ENVIRONMENT 

that  the  incomparable  mobihty  of  water, 
which  depends  upon  its  pecuhar  physical  prop- 
erties and  upon  its  existence  in  vast  quanti- 
ties in  all  three  states  of  solid,  liquid,  and 
gas,  is  the  chief  factor  among  the  properties  of 
matter  to  determine  the  nature  of  the  phenom- 

upon  the  presence  of  the  atmosphere,  upon  the  reHef  of  the 
land,  and  upon  the  radiant  energy  of  the  sun.  Through  the 
agency  of  rainfall,  of  surface  streams,  of  underground  waters, 
and  of  wave  action,  the  hydrosphere  is  constantly  modifying 
the  surface  of  the  hthosphere,  while  at  the  same  time  it  is 
bearing  into  the  various  basins  the  wash  of  the  land  and 
depositing  it  in  stratified  beds.  It  thereby  becomes  the 
great  agency  for  the  degradation  of  the  land  and  the  building 
up  of  the  basin  bottoms.  It  works  upon  the  land  partly  by 
dissolving  soluble  portions  of  the  rock  substance,  and  partly 
by  mechanical  action.  The  solution  of  the  soluble  part  usu- 
ally loosens  the  insoluble,  and  renders  it  an  easy  prey  of  the 
surface  waters.  These  transport  the  loosened  material  to 
the  valleys  and  at  length  to  the  great  basins,  meanwhile  roll- 
ing and  grinding  it  and  thus  reducing  it  to  rounder  forms  and  a 
finer  state,  until  at  length  it  reaches  the  still  waters  or  the  low 
gradients  of  the  basins  and  comes  to  rest.  The  hydrosphere 
is,  therefore,  both  destructive  and  constructive  in  its  action. 
As  the  beds  of  sediment  which  it  lays  down  follow  one  another 
in  orderly  succession,  each  later  one  lying  above  each  earlier 
one,  they  form  a  time  record.  And  as  relics  of  the  life  of 
each  age  become  more  or  less  imbedded  in  these  sediments, 
they  furnish  the  means  of  following  the  history  of  life  from 
age  to  age.  The  historical  record  of  geology  is,  therefore,  very 
largely  dependent  upon  the  fact  that  the  waters  have  thus 
buried  in  systematic  order  the  successive  life  of  the  ages." 
—  Chamberlin  and  Salisbury,  "Geology."  New  York, 
1904,  Vol.  I,  p.  8. 


WATER  75 

ena  which  he  studies;^  and    the  physiologist 
has  found  that  water  is  invariably  the  prin- 

^"Of  all  the  terrestrial  agents  by  which  the  surface  of 
the  earth  is  geologically  modified,  by  far  the  most  important 
is  water.  We  have  already  seen,  when  following  hypogene 
changes,  how  large  a  share  is  taken  by  water  in  the  phenom- 
ena of  volcanoes  and  in  other  subterranean  processes.  Re- 
turning to  the  surface  of  the  earth  and  watching  the  opera- 
tions of  the  atmosphere,  we  soon  learn  how  important  a  part 
of  these  is  sustained  by  the  aqueous  vapor  that  pervades 
the  atmosphere. 

"The  substance  which  we  term  water  exists  on  the  earth 
in  tlu-ee  well-known  forms:  (1)  gaseous,  as  invisible  vapor; 
(2)  liquid,  as  water;  and  (3)  solid,  as  ice.  The  gaseous 
form  has  already  been  noticed  as  one  of  the  characteristic 
ingredients  of  the  atmosphere.  Vast  quantities  of  vapor 
are  continually  rising  from  the  surface  of  the  seas,  rivers, 
lakes,  snow  fields,  and  glaciers  of  the  world.  This  vapor 
remains  invisible  until  the  air  containing  it  is  cooled  down 
below  its  dewpoint,  or  point  of  saturation,  —  a  result  which 
follows  upon  the  union  or  collision  of  two  aerial  currents  of 
different  temperatures,  or  the  rise  of  the  air  into  the  upper 
cold  regions  of  the  atmosphere,  where  it  is  chilled  by  expansion, 
by  radiation,  or  by  contact  with  cold  mountains.  Condensa- 
tion appears  only  to  take  place  on  free  surfaces,  and  the 
formation  of  cloud  and  mist  is  explained  by  condensation 
upon  the  fine  microscopic  dust  of  which  the  atmosphere  is 
full.  At  first  minute  particles  of  water  vapor  appear,  which 
either  remain  in  the  liquid  condition,  or,  if  the  temperature 
is  sufficiently  low,  are  frozen  into  ice.  As  these  changes  take 
place  over  considerable  spaces  of  the  sky,  they  give  rise  to 
the  phenomena  of  clouds.  Further  condensation  augments 
the  size  of  the  cloud  particles,  and  at  last  they  fall  to  the  sur- 
face of  the  earth,  if  still  liquid,  as  rain ;  if  solid,  as  snow  or 
hail;  if  partly  solid  and  partly  liquid,  as  sleet.  As  the 
vapor  is  largely  raised   from  the  ocean  surface,  so  in   great 


76      THE  FITNESS  OF  THE  ENVIRONMENT 

cipal  constituent  of  active  living  organisms.^ 
Water  is  ingested  in  greater  amounts  than  all 

measure  it  falls  back  again  directly  into  the  ocean.  A  con- 
siderable proportion,  however,  descends  upon  the  land,  and 
it  is  this  part  of  the  condensed  vapor  which  we  have  now 
to  follow.  Upon  the  higher  elevations  it  falls  as  snow,  and 
gathers  there  into  snow  fields,  which,  by  means  of  glaciers, 
send  their  drainage  towards  the  valleys  and  plains.  Else- 
where it  falls  chiefly  as  rain,  some  of  which  sinks  underground 
to  gush  forth  again  in  springs,  while  the  rest  pours  down  the 
slopes  of  the  land,  swelling  the  brooks  and  torrents  which, 
fed  both  by  springs  and  rains,  gather  into  broader  and  yet 
broader  rivers  that  bear  the  accumulated  drainage  of  the 
land  out  to  sea.  Thence  once  more  the  vapor  rises,  con- 
densing into  clouds  and  rain  to  feed  the  innumerable  water 
channels  by  which  the  land  is  furrowed  from  mountain  top 
to  seashore. 

"In  this  vast  system  of  circulation,  ceaselessly  renewed, 
there  is  not  a  drop  of  water  that  is  not  busy  with  its  allotted 
task  of  changing  the  face  of  the  earth.  "When  the  vapor 
ascends  into  the  air,  it  is,  comparatively  speaking,  chemi- 
cally pure.  But  when,  after  being  condensed  into  visible 
form,  and  working  its  way  over  or  under  the  surface  of  the 
land,  it  once  more  enters  the  sea,  it  is  no  longer  pure,  but  more 
or  less  loaded  with  material  taken  by  it  out  of  the  air,  rocks, 
or  soils  through  which  it  has  traveled.  Day  by  day  the 
process  is  advancing.  So  far  as  we  can  tell,  it  has  never  ceased 
since  the  first  shower  of  rain  fell  upon  the  earth.  We  may 
well  believe,  therefore,  that  it  must  have  worked  marvels 
upon  the  surface  of  our  planet  in  past  time,  and  that  it  may 
effect  transformation  in  the  future."  —  Geikie,  "Textbook 
of  Geology."     London,  1903,  4th  ed..  Vol.  I,  pp.  447,  448. 

^  Thus  water  makes  up  from  70  to  85  per  cent  of  fishes, 
about  87  per  cent  of  oysters,  85  per  cent  of  apples,  78  per 
cent  of  potatoes,  95  per  cent  of  the  edible  portion  of  lettuce, 
etc. 


WATER  77 

other  substances  combined,  and  it  is  no  less 
the  chief  excretion.  It  is  the  vehicle  of  the 
principal  foods  and  excretory  products,  for 
most  of  these  are  dissolved  as  they  enter  or 
leave  the  body.V  Indeed,  as  clearer  ideas  of 
the  physico-chemical  organization  of  proto- 
plasm have  developed  it  has  become  evident 
that  the  organism  itself  is  essentially  an 
aqueous  solution  in  which  are  spread  out  col- 
loidal substances  of  vast  complexity.^  As  a 
result  of  these  conditions  there  is  hardly  a 
physiological  process  in  which  water  is  not  of 
fundamental  importance. 

All  of  these  circumstances,  which  completely 
justify  the  interest  in  water  which  Thales  and 
Aristotle,  and  nearly  all  later  students  of  nature 
have  manifested,  depend  in  great  part  upon 
the  quantity  of  water  which  is  present  out- 
side the  earth's  crust,  and  upon  its  often 
unique    physical     and     chemical     properties. 

^  Properly  speaking,  the  entrance  of  the  foods  into  the 
body  is  across  the  wall  of  the  intestine;  at  this  point  the 
foods  have  all  undergone  digestion  and  are  almost  exclu- 
sively in  solution.  In  like  manner  excretion  takes  place 
across  the  renal  epithelium,  or  the  epithelium  of  the  lungs, 
or  across  that  of  the  sweat  glands ;  these  too  are  traversed 
only  by  substances  in  solution. 

2  "Der  Organismus,  Pflanze  wie  Tier,  ist  ein  Gefass  voll 
wasseriger  Losung,  in  dem  sich  als  disperse  Phase  verschieden- 
artige  Kolloide  befinden."  —  Bechhold,  "Die  Kolloide  in 
Biologic  und  Medizin."     Dresden,  1912. 


78      THE   FITNESS  OF  THE  ENVIRONMENT 

Such  properties  are  our  present  concern. 
Doubtless  if  it  were  not  for  the  enormous 
quantity  of  water  which  exists  upon  our 
planet,  all  its  physical  properties  would  be  of 
little  avail  to  bring  about  its  universal  im- 
portance in  nature.  This,  however,  as  has 
been  above  explained,  appears  to  be  neither 
an  accidental  nor  an  uncommon  phenomenon. 
.  Of  the  total  extent  of  the  earth's  surface 
the  oceans-make  up  about  three  fourths,  and 
they  contain  an  amount  of  water  sufficient, 
if  the  earth  were  a  perfect  sphere,  to  cover 
the  whole  area  to  a  depth  of  between  two  and 
three  miles.  This  corresponds  to  about  0.2  per 
cent  of  the  volume  of  the  globe.  The  occur- 
rence of  water  is,  moreover,  not  less  important 
and  hardly  less  general  upon  the  land.  In 
addition  to  lakes  and  streams,  water  is  al- 
most everywhere  present  in  large  quantities  in 
the  soil,  retained  there  mainly  by  capillary 
action,  and  often  at  greater  depths.  The 
atmosphere  also  contains  an  abundance  of 
water  as  aqueous  vapor  and  as  clouds.  Now 
the  very  occurrence  of  water  upon  the  earth, 
and  especially  its  permanent  presence,  is  due 
in  no  small  degree  to  its  chemical  stability 
in  the  existing  physical  and  chemical  con- 
ditions. This  stability  is  of  great  moment  in 
the  various  inorganic  and  organic  processes 


WATER  79 

in  which  water  plays  so  large  a  part.  In  the 
first  place  the  chemical  reactions  in  which  it 
is  concerned  during  the  process  of  geological 
evolution,  though  they  are  no  doubt  in  the 
total  of  great  magnitude,  are  both  slow  and 
far  from  violent.  Long  since  any  very  active 
changes  of  this  sort,  so  far  as  the  superficial 
part  of  the  crust  is  concerned,  have  run  their 
course.  In  the  second  place  water  is  really, 
at  the  temperature  of  the  earth  and  in  com- 
parison with  most  other  chemical  substances, 
an  extremely  inert  body,  for  the  union  of  hydro- 
gen with  oxygen  is  so  firm  that  it  is  not  readily 
dissolved. 

Thus  water  exists  as  a  singularly  inert  con- 
stituent of  the  atmosphere,  as  a  liquid  nearly 
inactive  in  chemical  processes  on  the  surface 
and  in  the  soil,  and  everywhere  as  a  mild  sol- 
vent which  does  not  easily  attack  the  sub- 
stances which  in  great  variety  dissolve  in  it. 
The  chemical  changes  which  do  follow  upon 
solution  are  not  such  as  to  produce  substan- 
tial chemical  transformations,  and  most  sub- 
stances can  pass  through  water  unscathed. 
The  nature  of  water,  then,  is  a  great  factor  in 
the  chemical  stability,  which,  no  less  than  the 
physical  stability  of  the  environment,  is  es- 
sential to  the  living  mechanism.  But  it  may 
be    questioned    if    such    stability    would    not 


80      THE  FITNESS  OF  THE  ENVIRONMENT 

necessarily  be  ultimately  attained  in  greater  or 
less  degree  with  almost  any  other  substance, 
as  a  result  of  the  general  tendency  of  chemical 
processes  to  reach  a  condition  of  equilibrium, 
and  it  will  therefore  be  well  to  turn  to  more 
secure  fields  of  inquiry. 


THERMAL  PROPERTIES 

The  most  familiar  among  such  are  certain 
characteristics  of  water  which  have  been  long 
known,  and  which,  as  the  Bridgewater  Trea- 
tises and  other  works  on  natural  theology 
testify,  were  formerly  favorite  subjects  of 
metaphysical  speculation, — the  thermal  prop- 
erties. These  characteristics  of  water  were 
recognized  at  an  early  stage  in  the  develop- 
ment of  modern  science,  and  in  many  cases 
their  special  importance  in  meteorology  and 
in  other  departments  of  the  sciences  of  nature 
is  almost  self-evident. 

A 

SPECIFIC  HEAT 

First  among  these  is  the  heat  capacity  or, 
as  it  is  more  commonly  termed,  the  specific 
heat  of  water.     This  quantity  has  the  value  of 


WATER  81 

1.000  for  the  interval  between  0°  and  1° 
centigrade,  a  number  which  is  due  to  the 
choice  of  water  in  defining  the  calorie  or 
fundamental  unit  of  heat.  The  calorie,  small 
calorie,  or  gram  calorie  is  that  quantity  of 
heat  which  is  required  to  raise  the  temperature 
of  one  gram  of  water  through  1°  centigrade, 
and  it  varies  slightly  with  the  temperature, 
having  the  relative  values  1.000  for  the  in- 
terval from  0°  to  1°,  0.998  for  the  interval  from 
4°  to  5°,  0.992  for  the  interval  from  15°  to 
16°,  and  its  mean  value  for  the  interval  from 
0°  to  100°  is  1.004.  The  heat  capacity  of 
water  is  then  1,000,  in  that  1.000  calorie  is  re- 
quired to  raise  the  temperature  of  1.000  gram 
of  water  through  1.000  degree  centigrade. 

The  approximate  specific  heats  of  a  variety 
of  important  substances  are  as  follows :  — 

Glass 0.20 

Sugar 0.30 

Ammonia,  liquid  .     .     .  1.23 

Chloroform 0.24 

Hydrogen 3.4 

Alcohol 0.5-0.7 

Hexane 0.50 

It  is  unnecessary  to  enter  upon  an  elaborate 
analysis  of  the  data  concerning  specific  heats, 
for  the  magnitude  of  the  specific  heat  of  a 
substance  is  dependent  upon  its  chemical 
nature,   as  was  first  made  clear  by   Dulong 


Hquid  .  . 
Water  I  sohd    .     . 

gas  .  . 
Lead 

.     .  1.00 
.     .  0.50 
.     .  0.3-0.5 
.     .  0.03 

Iron 

.     .  0.10 

Quartz     .... 

.     .  0  19 

Salt     .     . 

0  21 

Marble    .... 

.     .  0.22 

82      THE  FITNESS  OF  THE  ENVIRONMENT 

and  Petit  in  1819.  The  law  which  bears  their 
name  consists  of  the  statement  that  in  the 
case  of  elementary  substances  the  product  of 
specific  heat  and  atomic  weight  is  a  constant, 
—  roughly,  6.4,  Certainly  this  so-called  law 
is  a  mere  approximation,  and  some  elements, 
notably  carbon,  silicon,  and  boron,  at  the 
ordinary  temperature,  depart  widely  from  its 
requirements,  but  in  the  main  the  approxi- 
mation holds  good.  Later  the  researches  of 
Neumann,  Garnier,  Cannizaro,  and  especially 
of  Kopp  made  possible  an  extension  of  the  law 
to  compounds. 

It  is  evident  that  the  law  of  Dulong  and 
Petit  amounts  to  the  statement  that  for  all 
elementary  substances  the  quantity  of  heat 
which  is  required  to  change  the  temperature 
of  every  atom,  regardless  of  its  nature,  is  a 
constant.  A  brief  discussion  will  serve  to 
make  this  plain.  According  to  the  law  the 
specific  heat  of  an  element  varies  inversely 
as  its  atomic  weight,  diminishing  as  the  atomic 
weight  increases,  so  that  the  product  of  the 
two  quantities  remains  constant.  But  of 
course  the  number  of  atoms  per  gram  of  sub- 
stance also  varies  inversely  as  the  atomic 
weight.  Hence  the  specific  heats  of  elemen- 
tary substances  and  the  number  of  atoms  per 
gram  are  always  roughly  proportional,  which 


WATER 


83 


can  only  be  the  case  if  all  atoms,  no  matter 
of  what  element,  require  a  constant  amount  of 
heat  to  raise  their  temperatures  one  degree. 
That  is  to  say,  in  all  elementary  substances 
the  heat  capacity  of  the  atom  is  constant,  and 
independent  of  the  nature  of  the  element 
(with  the  qualifications  above  noted). 

The  study  of  compounds  has  shown  that 
this  same  generalization  is  also  true  of  them. 
This  means  that  in  all  substances  the  heat 
capacity  of  every  atom  is  nearly  constant  and 
is  independent  of  its  nature  and  of  that  of  the 
compound  in  which  it  finds  itself. 

Accordingly  the  law  of  Dulong  and  Petit 
may  be  formulated  as  follows ;  —  the  specific 
heat  of  a  substance  multiplied  by  the  average 
of  the  atomic  weights  of  all  the  constitutent 
atoms  in  the  molecule  is  often  equal  to  about 
6.4,  and  is  always  not  very  different  from  this 
number.  This  conclusion  may  be  tested  with 
the  data   above  recorded. 


Substance 

Molecular 
Weight 

Number 

OF 

Atoms 

Average 
Atomic 
Weight 

Specific 
Heat 

Specific  Heat 

X 

Atomic  Weight 

Water      . 

18 

3 

6 

1.0 

6.0 

Ammonia 

17 

4 

4 

1.2 

4.8 

Quartz     . 

60 

3 

20 

0.2 

4.0 

Salt    .     . 

58 

2 

29 

0.2 

5.8 

Sugar .     . 

342 

45 

8 

0.3 

2.4 

Hexane   . 

86 

20 

4 

0.5 

2.0 

84       THE  FITNESS  OF  THE  ENVIRONMENT 

It  must  be  confessed  that  such  data  are  not 
a  brilliant  confirmation  of  the  law.  A  series 
of  numbers  which  vary  from  2.0  to  6.0  is 
something  quite  different  from  constancy, 
and  every  one  of  these  numbers  is  less  than 
6.4.  It  is,  however,  certain  that  these  quanti- 
ties are  uniformly  of  the  same  order  of  magni- 
tude, and  this  is  all  that  is  of  importance  for 
our  present  purpose.  For  accordingly  they 
prove  that  unless  the  avea^age  atomic  weight 
of  a  substance  be  very  low  its  specific  heat 
cannot  be  very  high.  Of  course  only  com- 
pounds which  are  largely  made  up  of  hydrogen 
can  possess  very  low  average  atomic  weights, 
and  among  such  those  will  be  lowest  in  this 
respect  which  contain  a  relatively  small  number 
of  atoms  of  another  element  of  low  atomic 
weight,  like  carbon,  nitrogen,  oxygen,  etc. 
Of  such  substances  the  hydrocarbons  make  up 
the  only  numerous  group,  and  for  the  most 
part  their  specific  heats  appear  to  be,  like 
that  of  elementary  carbon  itself,  considerably 
lower  even  than  would  be  predicted  by  the 
rule.  So  it  is  that  the  conclusion  is  warranted 
that  water  shares  the  characteristic  of  very 
high  specific  heat  with  a  very  small  number  of 
substances,  among  which  hydrogen  and  am- 
monia are  probably  the  only  important  chemi- 
cal individuals.     From  this  conclusion  another 


WATER  85 

follows  directly ;  namely,  that  water  possesses 
certain  nearly  unique  qualifications  which 
are  largely  responsible  for  making  the  earth 
habitable,  or  at  least  very  favorable  as  a 
habitation  for  living  organisms. 

It  need  hardly  be  pointed  out  that  this 
importance  of  the  high  heat  capacity  of  water 
is  a  very  well-known  fact.  Even  in  the  early 
decades  of  the  nineteenth  century,  when 
natural  theology  and  argument  from  design 
were  the  subject  of  lively  controversy,  es- 
pecially in  England,  such  subjects  were  very 
familiar,  and  an  excellent  temperate  dis- 
cussion from  the  theologian's  side  will  be  found 
in  Whe  well's  Bridge  water  Treatise.^  At  that 
time,  before  a  clear  formulation  of  the  concept 
of  adaptation  existed,  it  was  of  course  impos- 
sible to  disentangle  such  natural  fitness  from 
the  results  of  the  organic  evolutionary  process. 
In  the  more  modern  period  since  the  publi- 
cation of  "The  Origin  of  Species,"  the  late 
Professor  J.  P.  Cooke  of  Harvard  has  dwelt 
upon  this  and  other  properties  of  water 
and  sought  to  show  that,  lying  wholly  apart 
from  the  new  ideas,  such  phenomena  remain 

^  Chapter  IX  of  this  work  deals  with  "The  Laws  of  Heat 
with  Respect  to  Water."  Although  the  ideas  are  somewhat 
vague,  the  importance  of  the  capacity  of  water  to  absorb 
heat  is  clearly  brought  out. 


86      THE  FITNESS  OF  THE  ENVIRONMENT 

unexplained  and  inexplicable  by  our  present 
laws  of  natural  science.  He,  too,  endeavored 
to  employ  such  facts  as  theological  arguments 
but,  in  spite  of  many  sound  contentions,  with 
less  success  in  a  more  skeptical  age.^ 

The  most  obvious  effect  of  the  high  specific 
heat  of  water  is  the  tendency  of  the  ocean  and 
of  all  lakes  and  streams  to  maintain  a  nearly 
constant  temperature.  This  phenomenon  is 
of  course  not  due  to  the  high  specific  heat 
of  water  alone,  being  also  dependent  upon 
evaporation,  freezing,  and  a  variety  of  cir- 
cumstances which  automatically  mix  and  stir 

""  water.  But  in  the  long  run  the  effect  of 
high  specific  heat  is  of  primary  importance. 
It  will  be  convenient  to  postpone  considera- 
tion of  the  regulation  and  importance  of  the 
constant  temperature  of  the  ocean  until  the 
other  properties  of  water  which  contribute 
thereto  have  been  discussed. 

—  A  second  effect  of  the  high  specific  heat  of 

^  "Assume  that  the  variations  preserved  by  natural  selec- 
tion are  all  accidental,  a  point  on  which  naturalists  greatly 
differ,  still  what  is  the  result  ?  An  adaptation  to  the  environ- 
ment. According  to  the  theory,  then,  the  conditions  of  the 
environment  are  a  determining  cause ;  and  unless  we  believe 
that  all  nature  was  the  result  of  a  fortuitous  concourse  of  atoms, 
we  can  find  in  these  conditions  abundant  opportunities  where 
intelligent  causation  can  act."  —  Josiah  Parsons  Cooke, 
"The  Credentials  of  Science."     New  York,  1888,  p.  251. 


WATER 


87 


water  is  the  moderation  of  both  summer  and 
winter  temperatures  of  the  earth.  It  is  not 
easy  to  estimate  the  total  magnitude  of  this 
effect,  but  the  manner  in  which  it  comes  about 
is  well  illustrated  by  the  differences  between 
seaboard  and  inland  climates  or  between  the 
climate  of  a  large  part  of  the  United  States, 
which  is  a  continental  climate,  and  that  of 
Western  Europe,  which  is  essentially  an  in- 
sular climate.  In  the  most  extreme  form 
such  moderation  of  climate  is  to  be  observed 
on  the  high  seas  and  upon  small  islands. 
There  are  found  the  smallest  known  differences 
between  the  mean  temperatures  of  different 
months  of  the  year  and  of  different  hours  of 
the  day,  and  the  least  tendency  to  violent 
changes  of  temperature.  The  calculation  of 
Zenker  regarding  normal   temperatures   may 


Latitude 

Continental  Climate 

Marine  Climate 

Difference 

Degrees 

Degrees 

Degrees 

Degrees 

0 

34.6 

26.1 

-8.5 

10 

33.5 

25.3 

-8.2 

20 

30.0 

22.7 

-7.3 

30 

24.1 

18.8 

-5.3 

40 

15.7 

13.4 

-2.3 

50 

5.0 

-7.7 

7.1 

2.1 

60 

0.3 

8.0 

70 

-19.0 

-5.2 

13.8 

80 

-24.9 

-8.2 

16.7 

90 

-26.1 

-8.7 

17.4 

88       THE  FITNESS  OF  THE  ENVIRONMENT 

be  cited  as  a  good  illustration  of  the  nature  of 
the  case.^ 

It  is  unnecessary  to  discuss  the  effects 
upon  living  organisms  of  the  equable  tem- 
perature of  the  ocean  and  of  the  moderation 
of  climate,  for  obviously  we  are  here  confronted 
by  a  true  instance  of  regulation  of  the  environ- 
ment. 

^*  The  high  heat  capacity  of  water  operates 
in  still  another  manner  to  regulate  tempera- 
ture upon  the  land  and  at  the  same  time  to 
increase  the  mobility  of  the  environment  of 
marine  organisms.  For  directly  or  indirectly 
it  is  involved  in  the  formation  and  duration 
of  ocean  currents,  especially  the  movement  of 
water  in  the  depths  from  the  polar  to  the 
tropical  seas,  and  it  determines  the  amount 
of  heat  carried  by  such  currents.  A  similar 
and  even  more  important  *' function"  is  the 
direct  promotion  of  winds,  with  the  resulting 
distribution  of  aqueous  vapor  throughout  the 
atmosphere,  a  primary  factor  in  the  dissemina- 
tion of  water  by  means  of  the  rainfall.  Here 
the  essential  thing  is  the  existence  of  a  vast 
warm  reservoir  in  the  tropics  and  of  two 
similar  cold   reservoirs  at  the  poles.     Under 

^  A  discussion  of  Zenker's  work  will  be  found  in  Hann's 
"Handbook  of  Climatology,"  translated  by  Ward,  pp.  210- 
215. 


WATER  89 

these  circumstances  the  circulation  of  winds, 
bearing  away  water  vapor  from  the  tropical 
oceans,  is  inevitable,  and  the  process  is 
intensified  by  the  high  specific  heat  of 
water. 

The  living  organism  itself  is  directly  favored 

by  this  same  property  of  its  principal  constit- 
uent, because  a  given  quantity  of  heat  pro- 
duces as  little  change  as  possible  in  the  tem- 
perature of  its  body.  Man  is  an  excellent 
case  in  point.  An  adult  weighing  75  kilo- 
grams (165  pounds)  w^hen  at  rest  produces 
daily  about  2400  great  calories,  which  is  an 
amount  of  heat  actually  sufficient  to  raise 
the  temperature  of  his  body  more  than  32° 
centigrade.  But  if  the  heat  capacity  of  his 
body  corresponded  to  that  of  most  substances, 
the  same  quantity  of  heat  .would  be  suflScient 
to  raise  his  temperature  between  100°  and 
150°.  In  these  conditions  the  elimination  of 
heat  would  become  a  matter  of  far  greater 
difficulty,  and  the  accurate  regulation  of  the 
temperature  of  the  interior  portion  of  his  body, 
especially  during  periods  of  great  muscular 
activity,  well-nigh  impossible.  Extreme  con- 
stancy of  the  body  temperature  is,  of  course, 
a  matter  of  vital  importance,  at  least  for  all 
highly  organized  beings,  and  it  is  hardly 
conceivable  that  it  should  be  otherwise.     In 


90      THE  FITNESS   OF  THE  ENVIRONMENT 

the  first  place  marked  influence  of  change  of 
temperature  upon  chemical  reaction  is  almost 
universal,  and  as  a  rule  an  increase  of  10° 
centigrade  in  temperature  will  more  than 
double  the  rate  of  a  chemical  change.^  Sec- 
ondly all  living  organisms  contain  both  chemi- 
cal substances  and  physico-chemical  struc- 
tures or  systems  which  begin  to  be  altered, 
and  usually  irreversibly  altered,  at  a  tempera- 
ture which  is  very  little  above  that  of  the 
human  body.^     It  is  perhaps  imaginable  that 

^  If  the  velocity  of  a  chemical  reaction  be  represented  by 
a  coefficient,  k,  the  increase  in  its  magnitude  with  rising  tem- 
perature is  unlike  that  of  ordinary  physical  coefficients,  and 
in  many  cases  amounts  to  a  two  or  threefold  rise  for  a  tem- 
perature increase  of  10°  centigrade.  The  well-known  data 
concerning  the  transformation  of  dibromsuccinnic  acid  into 
brommaleic  acid  and  hydrobromic  acid  in  aqueous  solution 
illustrate  a  typical  case. 


t 

h 

15° 

0.00000967 

40° 

0.0000863 

50° 

0.000249 

60.2° 

0.000654 

70.1° 

0.00169 

80° 

0.0046 

89.4° 

0.0156 

101° 

0.0318 

^  This  is  attested  not  only  by  the  low  temperature  at 
which  many  proteins  coagulate,  but  also  by  the  action  of 
temperatures  between  50°  and  60°  to  inactivate  enzymes,  and 


WATER  91 

conditions  might  be  otherwise  in  beings  of  a 
very  different  kind,  but  to-day  every  chemist 
well  knows  that  if  he  is  to  control  a  chemical 
process,  almost  the  first  desideratum  is  rigid 
regulation  of  the  temperature  at  which  the 
process  takes  place. ^ 

It  is  therefore  incontestable  that  the  un- 
usually high  specific  heat  of  water  tends 
automatically  and  in  most  marked  degree  to 
regulate  the  temperature  of  the  whole  envi- 
ronment, of  both  air  and  water,  land  and  sea, 
and  that  of  the  living  organism  itself.  Like- 
wise the  same  property  favors  the  circulation 
of  water  by  facilitating  the  production  of 
winds,  besides  contributing  to  the  formation 
of  ocean  currents.  Here  is  a  striking  instance 
of  natural  fitness,  which  in  like  degree  is  un- 
attainable with  any  other  substance  except 
ammonia. 

to  produce  alterations  in  many  of  the  complex  substances 
that  are  involved  in  the  phenomena  of  immunity  and  other 
similar  things. 

^  Almost  the  most  conspicuous  change  in  the  equipment 
of  modern  chemical  laboratories,  as  a  result  of  the  growth  of 
physical  chemistry,  is  the  introduction  everywhere  of  thermo- 
stats. 


92       THE  FITNESS  OF  THE  ENVIRONMENT 

B 

LATENT  HEAT 

Very  different  from  specific  heat  in  their 
relationship  to  the  chemical  constitution  of 
a  substance,  but  not  unlike  it  in  biological 
importance,  are  the  so-called  latent  heats  of 
melting  and  of  evaporation. 
^  The  latent  heat  of  melting  is  expressed  as 
the  number  of  calories  which  are  required  to 
convert  one  gram  of  solid  at  the  freezing  point 
into  one  gram  of  liquid  at  the  same  tempera- 
ture. For  water  its  value  is  approximately 
80,  which  indicates  that  the  same  quantity 
of  heat  must  be  employed  to  melt  ice  as  to 
raise  the  temperature  of  the  resulting  ice- 
_  water  to   80°  centigrade. 

The  latent  heat  of  evaporation  is  similarly 
defined  as  the  number  of  calories  required  to 
change  one  gram  of  liquid  into  vapor.  Its 
magnitude  depends  upon  the  temperature  at 
which  the  process  takes  place.  The  latent 
heat  of  evaporation  of  water  is  approximately 
536.  There  is  required,  accordingly,  as  much 
heat  to  boil  away  one  gram  of  water  as  to 
raise  the  temperature  of  536  grams  through  1° 
centigrade. 

There  are  a  number  of  important  effects  of 


WATER  93 

the  high  latent  heats  of  fusion  and  evapora- 
tion of  water  upon  the  meteorological  pro- 
cesses. When,  for  example,  a  body  of  water 
becomes  cooled  to  its  freezing  point,  the 
further  abstraction  of  heat  cannot  lower  its 
temperature  below  that  point,  which,  to  be 
sure,  is  somewhat  variable  in  the  case  of  salt 
water.  And  so  long  as  water  and  ice  exist 
in  contact,  the  system  constitutes  a  ther- 
mostat, a  very  accurate  one  if  the  water  be 
fresh,  which  changes  only  in  respect  to  the 
quantities  of  ice  and  water  as  heat  is  added  or 
removed.^  Heating  serves  merely  to  melt 
the  ice,  cooling  to  freeze  the  water.  Accord- 
j  ngly,  as  long  as  the  earth  shall  remain  habit- 
able the  cooling  of  its  oceans  and  seas  will 
remain  rigidly  limited  by  their  freezing  point. 
However  inclement  the  atmosphere,  the  ocean 
can  always  support  life  until  the  final  extinc- 
tion of  water  by  cold.  It  is  worthy  of  note 
that  the  freezing  point  of  water,  though  to 
j'lan  with  his  carefully  regulated  body  tem- 
perature apparently  low%  is  in  reality  very 
high  indeed  compared  with  that  of  any  like 
.substances,  —  perhaps  100°  centigrade  above 
t  he  average. 

^  In  fact,  there  is  no  better  means  of  obtaining  a  constant 
temperature  in  the  chemical  laboratory  than  by  mixing  pure 
ice  with  pure  water. 


94       THE   FITNESS  OF  THE   ENVIRONMENT 
Table  of  Melting  Points 

Degrees 


Water 

Hydride  of  antimony  . 
Hydride  of  arsenic  .  . 
Hydrobromic  acid  .  . 
Hydrochloric  acid  .  . 
Hydrofluoric  acid  .  . 
Hydriodic  acid     .     .     . 

Methane 

Carbon  dioxide     .     .     . 
Hydride  of  phosphorus 
Hydrogen  sulphide   .     . 
Sulphurous  oxide .     .     . 

Ammonia 

Nitric  oxide     .... 


0 

-91.5 
-113.5 

-87 
-112.5 

-92.3 

-50 
-185.8 

-  57 
-132.5 

-85.6 

-72.7 

-75 
-167 


This  is,  no  doubt,  one  of  the  most  important 
facts  with  which  we  are  concerned,  for  while  a 
very  large  number  of  chemical  processes  take 
place  quite  freely  at  0°,  the  conditions  are 
very  different  at  the  freezing  point  of  am- 
monia, for  instance.  At  that  temperature  the 
velocity  of  most  chemical  processes  is  but  a 
fraction  of  one  per  cent  of  their  velocity  at 
0°,  and  a  large  part  of  the  chemical  activity 
which  is  familiar  to  us  ceases. 

The  result  of  the  unusually  high  freezing, 
point  of  water  and  of  the  phenomenon  of 
latent  heat  is  felt,  however,  not  merely  in  the 
avoidance  of  an  excessive  fall  in  the  tempera- 
ture of  lakes  and  seas.     As  above  explained, 


WATER 


95 


whenever  the  ocean  comes  in  contact  with 
cHmates  of  very  low  temperature  it  tends  to 
moderate  them,  the  more  effectively  the 
greater  the  disparity  between  the  temperature 
of  the  air  and  that  of  the  water,  and  here 
latent  heat  is  quite  as  important  a  factor, 
though   indirectly,   as   specific  heat. 

It  remains  to  point  out  that  the  latent  heat 
of  melting  of  water  is  nearly  the  greatest 
which  has  yet  been  discovered,  being  ex- 
ceeded, in  fact,  by  that  of  ammonia  alone. 

Table  of  Latent  Heats  of  Melting 


Substance 


Lead  .... 
Bromine  .  .  . 
Cadmium  .     .     . 

Iron 

Gallium  .  .  . 
Iodine  ... 
Potassium .  .  . 
Copper .... 
Sodium  .  .  . 
Nickel  .... 
Palladium .  .  . 
Phosphorus  .  . 
Platinum  .  .  . 
Mercury  .  .  . 
Sulphur  .  .  . 
Silver  .... 
Bismuth     .     .     . 

Zinc 

Tin 


Formula 

Melting 
Point 

Latent  Heat 
OF  Fusion 

Pb 

326° 

5,4     Calories 

Br 

-7.3 

16.2 

Cd 

321 

13.7 

Fe 

23-33 

Ga 

13 

19.1 

I 

11.7 

K 

58 

15.7 

Cu 

43 

Na 

96.5 

31.7 

Ni 

4.64 

Pd 

36.3 

P 

27.35 

4.7 

Pt 

1779 

27.18 

Hg 

2.82 

S 

115 

9.37 

Ag 

999 

21.07 

Bi 

266.8 

12.64 

Zn 

415 

28.13 

Sn 

233 

14.25 

96      THE   FITNESS  OF  THE  ENVIRONMENT 


Substance 

Formula 

Melting 
Point 

Latent  Heat 
OF  Fusion 

Water 

H2O 

0° 

80    Calories 

Ammonia  .     .     .     . 

NH3 

-75 

108 

Antimony  chloride  . 

SbCla 

73 

13.4 

Antimony  bromide . 

SbBrg 

94 

9.7 

Lead  chloride      ,     . 

PbCl2 

485 

20.9 

Calcium  chloride     . 

CaCl2-6H20 

28.5 

40.7 

Potassium  nitrate    . 

KNO3 

339 

47.4 

Sodium  nitrate   .     . 

NaNOs 

310.5 

63 

Phosphoric  acid 

H3PO4 

18 

25.7 

Nitric  acid     .     .     . 

HNO3 

-47° 

9.5 

Sulphuric  acid    .     . 

H2SO4 

10.3 

24. 

Sulphuric  oxide  .     . 

SO3 

76.7 

Ethylene  bromide  . 

C2H4Br2 

8 

13 

Formic  acid   .     .     . 

H.COOH 

-7.5 

57.4 

Chloral  hydrate 

C2H3CI3O2 

46 

33.2 

Dimethyl  oxalate    . 

C204(CH3)2 

49.5 

42.6 

Acetic  acid     .     ,     . 

CH3COOH 

43.7 

Glycerine  .... 

C3H8O3 

13 

42.5 

Stearic  acid    .     .     . 

C18H36O2 

64 

47.6 

Benzene     .... 

CeHe 

5.3 

30.1 

Nitrobenzene      .     . 

C6H5NO2 

-9.21 

22.3 

Di-chlorbenzene 

C6H4CI2 

52.5 

29.9 

p-Toluidine    .     .     . 

C7H9N 

35.8 

Phenol       .     .     .     . 

CeHsOH 

25.4 

24.9 

Menthol    .     .     .     . 

C10H20O 

42 

18.9 

Phenylhydrazine     . 

C6H5.NH.NH2 

24.5 

Phenylacetic  acid    . 

C6H5.CH2.COOH 

75 

25.4 

Naphthahne  .     .     . 

CioHs 

80 

35.7 

Accordingly,  the  processes  above  described 
possess  nearly  the  highest  possible  efficiency. 
A  very  large  amount  of  heat  must  be  ab- 
stracted from  a  body  of  water  before  it  can 
be  solidified ;    after  a  given  amount  of  cool- 


WATER  97 

ing  a  very  large  quantity  of  water  must  re- 
main liquid ;  a  body  of  water  at  0°  centi- 
grade can  warm  up  a  very  large  amount  of 
colder  air  with  the  formation  of  a  very  small 
quantity  of  ice.  Thus  the  permanency  of 
the  ocean,  and  the  moderating  effect  of  water 
upon  cold  climates  are  very  nearly  maximal. 
These  are  also  facts,  directly  dependent  upon 
the  physico-chemical  nature  of  water,  which 
are  remarkably  favorable  to  the  organism. 

Still  more  important  is  the  latent  heat  of 
evaporation  of  water.  Wherever  water  is 
in  contact  with  the  air,  evaporation  must  take 
place  until,  if  the  system  be  of  small  dimen- 
sions, equilibrium  is  established  between  aque- 
ous vapor  and  the  liquid;  in  short  until  the 
air  is  saturated  with  water.  Unlike  freezing, 
which  occurs  only  at  one  particular  tempera- 
ture, this  process  goes  on  continuously  through- 
out all  ranges  of  temperature  at  which  liquid 
water  can  exist,  and  even  upon  ice  at  low  tem- 
peratures. It  is  always  accompanied  by  the 
conversion  of  heat,  in  the  amount  measured 
by  the  latent  heat  of  evaporation,  into  other 
forms  of  energy ;  the  heat  becomes  latent. 
And  since  air  in  contact  with  water  is  rarely 
saturated  with  aqueous  vapor,  owing  to  the 
constant  movement  of  the  atmosphere,  the 
process  of  evaporation,  with  the  accompany- 


98       THE   FITNESS  OF  THE  ENVIRONMENT 

ing  conversion  of  heat  into  latent  heat,  is  a 
continuous  process.  The  phenomenon  is  a 
variable  one,  however,  for  while  at  high  tem- 
perature, both  because  of  the  greater  supply 
of  heat  and  because  of  the  greater  amount  of 
water  vapor  that  the  air  can  hold,  the  process 
is  very  important  and  active,  at  low  tem- 
perature it  is  far  less  considerable.  This  in 
itself  is  no  doubt  a  benefit  because  it  tends 
especially  to  restrict  the  upward  march  of 
temperature  when  the  temperature  is  high, 
but  is  of  minor  importance  when  the  tempera- 
ture is  low. 

In  view  of  the  other  favorable  qualities  of 
water  it  is  perhaps  not  surprising  to  find  that 
its  latent  heat  of  evaporation  is  by  far  the 
highest  known.  So  great,  in  truth,  is  this 
quantity  and  so  important  the  process  that 
the  latent  heat  of  evaporation  is  one  of  the 
most  important  regulatory  factors  at  present 
known  to  meteorologists. 

When  the  sun  shines  upon  a  body  of  water, 
only  a  small  part  of  the  energy  which  the 
water  receives  contributes  to  the  elevation  of 
its  temperature.  Thus  Fitzgerald  has  con- 
cluded from  his  studies  of  Lough  Derg  in 
Ireland  during  clear   hot    summer   weather  ^ 

1  See  Hann,  "Handbook  of  Climatology,"  translated  by 
Ward,  p.  131. 


WATER  99 

Table  of  Latent  Heats  of  Evaporation 


Temper- 

Sub TANCE 

Formula 

ature  OF 
Vapor- 
ization 

Latent  Heat  of 
Vaporization 

Water 

H2O 

100° 

536     Calories 

Ammonia 

NH3 

295 

Bromine 

Bra 

61.5 

43.7 

Chlorine 

CI2 

-22 

67.4 

Iodine 

I2 

174 

23.9 

Hydrofluoric  acid   .     . 

HF 

360 

Oxygen     

O2 

-188 

58 

Nitrogen 

N2 

49.8 

Phosphorus   .     ,     .     . 

P 

287 

130.4 

Mercury 

Hg 

350 

62 

Sulphur 

S2 

316 

362 

Nitrous  oxide     .     .     . 

N2O 

100.6 

Nitric  acid     .... 

HNO3 

115 

Sulphurous  oxide    .     . 

SO2 

'      0 

91.2 

Sulphuric  oxide .     .     . 

SO3 

18 

147.5 

Sulphuric  acid   .     .     . 

H2SO4 

326 

122.1 

Thionylchloride      .     . 

SOCI2 

82 

54.5 

Arsenic  chloride      .     . 

AsCl3 

69.7* 

Phosphorus  trichloride 

PCI3 

67.2* 

Stannic  chloride      .     . 

SnCL, 

46.8* 

Silicon  chloride  .     .     . 

SiCL, 

37.3 

Carbon  dioxide  .     .     . 

CO2 

72.2 

Carbon  disulphide  .     . 

CS2 

0 

90 

Carbon  tetrachloride  . 

CCI4 

0 

52 

Cyanogen 

(CN)2 

0 

103 

Hydrocyanic  acid  .     . 

HCN 

20 

211* 

Methyl  alcohol  .     .     . 

CH3OH 

0° 

289.2 

Ethyl  alcohol     .     .     . 

C2H5OH 

0 

236.5 

Amyl  alcohol     .     .     . 

CsHuOH 

131 

120 

Cetyl  alcohol      .     .     . 

C16H33OH 

58.5 

Hexane 

C6H14 

68 

79.4 

Methyl  chloride     .     . 

CH3CI 

0 

96.9 

*  Total  heat  of  vaporization. 


100     THE  FITNESS  OF  THE  ENVIRONMENT 


Temper- 

Substance 

FORMXJLA 

ature  OF 
Vapor- 
ization 

Latent  Heat  op 
Vaporization 

Ethyl  bromide   .     .     . 

CaHaBr 

38.2 

60.4  Calories 

Amyl  iodide  . 

CsHuI 

47.5 

Aldehyde  . 

CH3.CHO 

136.4 

Chloroform 

CHCI3 

0 

67 

Ether   .     . 

(C2H5)20 

34.9 

90.4 

Acetone    . 

CH3.CO.CH3 

56.6 

125.3 

Formic  acid 

HCOOH 

103.7 

Acetic  acid 

CH3COOH 

118 

84.9 

Acetic  anhydride 

(CH3CO)20 

137 

66.1 

Dichlor-acetic  acid 

CHCI2COOH 

138.4 

79.1 

Valerianic  acid  . 

C5H10O2 

103.5 

Ethyl  acetate 

C4H7O2 

105.8 

Acetyl  chloride 

CH3COCI 

78.9 

Acetonitrite  . 

CHaCN 

81.5 

170.6 

Ethyl  amine  . 

C2H5NH2 

146.2 

Benzene    .     . 

CeHe 

0 

109 

Toluene    .     . 

C6H5CH3 

111 

83.5 

Nitro-benzene 

C6H5NO2 

151.5 

79.1 

Aniline      .     . 

C6H5NH2 

93.3 

Acetophenone 

C6H5COCH3 

203.7 

77.2 

Benzonitrite  . 

C6H5CN 

191 

87.7 

Piperidine 

CsHiiN 

105.8 

88.9 

Pyridine    .     . 

C5H5N 

115.5 

101.4 

that  in  the  morning  the  surface  temperature 
rises  about  0.6°  per  hour.  This,  however, 
appears  to  account  for  but  a  small  fraction 
of  the  solar  heat  which  the  lake  had  taken 
up ;  the  rest  must  have  been  expended  in 
evaporation.  Another  element  of  great  im- 
portance is  the  transparency  of  water.  As  a 
result  the  rays  of   the  sun  are  not  absorbed 


WATER  101 

by  the  mere  surface  alone,  but  a  considerable 
layer  of  water  near  the  surface  receives  the 
heat. 

At  the  equator  the  evaporation  of  the  ocean 
appears  to  be  about  2.3  meters  per  year,^ 
which  involves  more  than  1,000,000,000,000,- 
000  calories  of  latent  heat  per  square  kilo- 
meter. The  amount  of  heat  which  is  em- 
ployed in  evaporating  water  from  100  square 
kilometers  of  the  tropical  ocean  is  accordingly 
vastly  more  than  all  the  energy  employed  in 
the  metabolism  of  the  total  population  of 
the  United  States,  and  it  amounts  to  more 
than  100,000,000  horse  power.  This  is  equiv- 
alent to  more  than  one  horse  power  per  square 
meter  day  and  night  throughout  the  year. 
To  a  greater  or  less  extent  all  over  the  earth 
this  same  process  goes  on,  and  as  a  result  the 
water  vapor  in  the  air  probably  averages 
between  15  and  20  kilograms  per  square  meter 
of  the  earth's  surface,  an  ample  supply  for 
the  formation  of  rain.  The  effect  of  this 
enormous  evaporation  to  moderate  the  tem- 
perature of  the  tropics  is  very  considerable ; 
but  the  heat  which  thus  disappears  is  not 
lost.  Rendered  latent  at  the  place  of  evap- 
oration, it  is  turned  back  into  actual  heat  at 

^  This  and  other  similar  facts  will  also  be  found  in  the 
work  of  Hann. 


102     THE  FITNESS  OF  THE  ENVIRONMENT 

the  point  of  condensation,  and  thus  serves 
to  warm  another  and  cooler  locality. 

This  process,  so  vast  that  all  the  water  power 
of  the  globe  may  be  regarded  as  its  secondary 
by-product,  possesses,  in  respect  to  its  ten- 
dency to  moderate  and  equalize  the  temper- 
ature of  ocean,  of  lakes,  and  of  the  climates 
of  all  the  earth,  a  maximal  value.  No  other 
liquid  could,  during  the  evaporation  of  a 
given  quantity  of  material,  bind  so  much  heat; 
no  other  vapor  could  yield  so  much  heat  upon 
condensation. 

Quite  as  important  to  man  as  this  great 
power  of  meteorological  regulation  is  the 
corresponding  physiological  activity,  evap- 
oration of  water  from  the  skin  and  lungs. 
In  an  animal  like  man,  whose  metabolism  is 
very  intense,  heat  is  a  most  prominent  ex- 
cretory product,  which  has  constantly  to  be 
eliminated  in  great  amounts,  and  to  this  end 
only  three  important  means  are  available: 
conduction,  radiation,  and  the  evaporation  of 
water.  The  relative  usefulness  of  these  three 
methods  varies  with  the  temperature  of  the 
environment.  At  a  low  temperature  there 
is  little  evaporation  of  water,  but  at  body 
temperature  or  above  there  can  be  no  loss  of 
heat  at  all  by  conduction  and  radiation,  and 
the  whole  burden  is  therefore  thrown  upon 


WATER  103 

evaporation.  The  manner  in  which  evapora- 
tion becomes  important  in  temperature  reg- 
ulation is  well  illustrated  by  the  following  cal- 
culation from  a  chart  of  Rubner's.^  The 
experiments  upon  which  the  chart  is  based 
were  made  upon  the  dog,  an  animal  which 
lacks  man's  apparatus  of  sweat  glands.  The 
values  of  the  table  are  only  approximate. 


Temperature 

Heat  Loss  by  Evaporation 

Degrees 

Per  Cent 

9 

16 

11 

19 

13 

22 

15 

25 

17 

27 

19 

30 

21 

32 

23 

32 

27 

36 

29 

42 

31 

58 

33 

64 

35 

79 

In  plants  evaporation  is  even  more  impor- 
tant than  in  animals.  Evidently  such  adap- 
tation of  the  physiological  processes  to  the 
conditions  of  the  environment  is  enormously 
favored  by  the  high  latent  heat  of  evapora- 
tion.^ 

^  Lusk,  "The  Science  of  Nutrition,"  p.  99. 
2  A  full  discussion  of  this  subject  will  be  found   in    the 
work  of  Lusk  (see  above),  Chap.  Ill,  especially  pp.  98-100. 


104      THE  FITNESS  OF  THE  ENVIRONMENT 

There  is  still  another  beneficial  result  of 
this  property :  the  great  variation  in  the  vapor 
tension  of  water  which  accompanies  variation 
in  temperature.  Vapor  tension  measures  the 
amount  of  vapor  which  is  present  in  the 
atmosphere  when  it  is  in  contact  with  a  liquid 
and  after  it  has  become  saturated  with  the 
liquid's  vapor.  Now,  according  to  a  well- 
known  law,  the  rate  of  increase  of  vapor  ten- 
sion, or  in  other  words  the  amount  of  vapor 
which  the  air  can  hold,  is  greater  the  greater 
the  latent  heat  of  vaporization.^  Hence, 
degree  by  degree  there  is  more  variation  in 
the  vapor  tension  of  water  than  there  could 
be  if  the  latent  heat  were  lower.  Such  great 
variability  in  the  quantity  of  water  which 
the  air  can  hold  is  in  meteorology  the  most 
important  characteristic  of  aqueous  vapor.^ 
The  relationship  between  vapor  tension  and 
temperature  (centigrade)  is  shown  in  the 
accompanying  table. 

^  Near  the  freezing  point  an  increase  of  10°  in  temperature 
doubles  the  amount  of  water  which  the  air  can  hold.  The 
increase  is  proportional  to  the  latent  heat  of  vaporization 
according  to  the  formulae 

,.3025  log  Ei  =  l«l^f^^) 
^  PC       1.99  V  ToTi  J 

where  W  stands  for  the  latent  heat  of  vaporization,  p  for  vapor 

tension,  and  T  for  temperature. 

^  Arrhenius,  "Kosmische  Physik,"  p.  612. 


WATER 

Temperature 

Vapor  Tension 

Degrees 

Millimeters 

0 

4.58 

10 

9.18 

20 

17.41 

30 

31.55 

40 

54.97 

50 

92.17 

80 

355.47 

90 

526.00 

100 

760.00 

105 


These  variations  are  what  make  possible  both 
the  evaporation  of  water  and  its  precipitation 
as  rain  and  as  dew  in  the  meteorological  cycle. 
And  therefore  the  high  latent  heat  of  vapori- 
zation of  water  is  in  still  another  manner  a 
most  favorable  circumstance  in  its  effect  upon 
the  organisms. 

To  sum  up,  this  property  appears  to  possess 
a  threefold  importance.  First,  it  operates 
powerfully  to  equalize  and  to  moderate  the 
temperature  of  the  earth;  secondly,  it  makes 
possible  very  effective  regulation  of  the  tem- 
perature of  the  living  organism;  and  thirdly, 
it  favors  the  meteorological  cycle.  All  of 
these  effects  are  true  maxima,  for  no  other 
lubstance  can  in  this  respect  compare  with 
water.  ^ 

^  This  conclusion  may  be  contrasted  with  that  of  Whewell 
(Bridgewater  Treatise,  p.  142).  He  includes  the  expansion  of 
water  by  heat,  the  expansion  of  water  by  cold  below  40°,  the 
expansion  of  water  in  freezing,  the  latent  heats  of  melting  and 


106     THE  FITNESS  OF  THE  ENVIRONMENT 

c 

THERMAL  CONDUCTIVITY 

The  heat  conduction  of  water  is  also  a  maxi- 
mum among  ordinary  liquids,  and,  though 
very  low  compared  with  good  conductors  like 
metals,  must  favor  the  equalization  of  tempera- 
ture within  the  living  cells  whose  structure  hin- 
ders the  establishment  of  convection  currents. 

Table  of  Heat  Conductivities 

Water        0.0125  Rubber 0.0004 

Alcohol 0.00048  Tin 0.15 

Ether         0.00034  Lead 0.08 

Benzene 0.00033  Iron 0.16 

Glycerine 0.00066  Copper 0.72 

Crown  glass        ....  0.0016  Silver 1.10 

D 

EXPANSION  BEFORE  FREEZING 

A  final  thermal  property  of  water  remains 
to  be  considered;  namely,  its  anomalous  ex- 
pansion when  cooled  at  temperatures  near 
the  freezing  point.  The  facts  are  illustrated 
by   the   accompanying   table. 

evaporation,  and  the  rate  of  evaporation  of  water.  It  will 
be  seen  that  eighty  years  ago  it  was  already  possible  to 
make  out  a  strong  case  for  the  fitness  of  water ;  but  it  should 
not  be  forgotten  that  at  that  time  ideas  were  in  some  respects 
still  very  vague,  and  comparative  data  few. 


WATER 


107 


Temperature 

Density  of  Water 

Expansion  From  4° 

Per  cent 

0 

0.99987 

0.013 

1 

0.99993 

0.007 

2 

0.99997 

0.003 

3 

0.99999 

0.001 

4 

1.00000 

0.000 

5 

0.99999 

0.001 

6 

0.99997 

0.003 

7 

0.99993 

0.007 

8 

0.99988 

0.012 

9 

0.99981 

0.019 

10 

0.99973 

0.027 

20 

0.99824 

0.176 

30 

0.99567 

0.44 

40 

0.99233 

0.77 

50 

0.98813 

1.19 

100 

0.95934 

4.07 

This  unique  property  of  water  is  the  most 
famihar  instance  of  striking  natural  fitness  of 
the  environment,  although  its  importance 
has  perhaps  been  overestimated.^  If,  how- 
ever, water,  like  all  other  common  substances, 

^  It  scarcely  merits  the  curious  rhapsody  of  Prout,  for 
instance :  "The  above  anomalous  properties  of  the  expan- 
sion of  water  and  its  consequences  have  always  struck  us  as 
presenting  the  most  remarkable  instances  of  design  in  the 
whole  order  of  nature  —  an  instance  of  something  done  ex- 
pressly, and  almost  (could  we  indeed  conceive  such  a  thing 
of  the  Deity),  at  second  thought,  to  accomplish  a  particular 
object."  —  Prout,  Bridgewater  Treatise,  "  Chemical  Meteor- 
ology and  the  Function  of  Digestion."  London,  1834,  pp. 
249-250. 


108     THE  FITNESS  OF  THE  ENVIRONMENT 

steadily  contracted  on  cooling,  so  that  its 
point  of  maximum  density  fell  at  the  freezing 
point,  it  is  impossible  to  say  how  great  would 
be  the  disadvantage  for  living  organisms. 
Certain  it  is  that  life  upon  the  earth  would  be 
thereby  very  greatly  restricted.  For  this  prop- 
erty, together  with  the  by  no  means  unique  phe- 
nomenon of  expansion  upon  solidification,^  is 
very  largely  responsible  for  the  permanence 
in  liquid  state  of  many  bodies  of  water  in 
cold  climates.  In  salt  water  the  anomalous 
contraction  disappears,  and  the  lack  of  paleo- 
crystic  ice  is  due  to  the  density  of  ice  and  to 
the  great  mass  of  the  ocean  and  the  movement 
of  its  waters.^ 

There  is  an  old  experiment  of  Rumford's 
which  well  illustrates  what  conditions  must 
have  been  had  the  contraction  of  water  been 
normal  and  ice  denser  than  water.^  He 
found  that  in  a  vessel  filled  with  water,  which 
contains  ice  confined  at  the  bottom,  it  is 
possible  to  heat  and  even  boil  the  superficial 
portion  of  the  water  without  melting  the  ice. 
And  so  it  would  be  with  lakes,  streams,  and 
oceans  were  it  not  for  the  anomaly  and  the 

^  The  density  of  ice  at  the  melting  point  is  0.91674. 
2  A  full   discussion   of   this   subject  will  be  found   in    S. 
Gunther's  "Handbuch  der  Geophysik." 
2  See  Whewell's  Bridgewater  Treatise. 


WATER  109 

buoyancy  of  ice.  The  coldest  water  would 
continually  sink  to  the  bottom  and  there 
freeze.  The  ice,  once  formed,  could  not  be 
melted,  because  the  warmer  water  would  stay 
at  the  surface.  Year  after  year  the  ice  would 
increase  in  winter  and  persist  through  the 
summer,  until  eventually  all  or  much  of  the 
body  of  water,  according  to  the  locality, 
would  be  turned  to  ice.  As  it  is,  the  tempera- 
ture of  the  bottom  of  a  body  of  fresh  water 
cannot  be  below  the  point  of  maximum  den- 
sity ;  on  cooling  further  the  water  rises ; 
and  ice  forms  only  on  the  surface.  In  this 
way  the  liquid  water  below  is  effectually  pro- 
tected from  further  cooling,  and  the  body  of 
water  persists.  In  the  spring  the  first  warm 
weather  melts  the  ice,  and  at  the  earliest 
possible  moment  all  ice  vanishes. 

Such  are  the  important  thermal  properties 
of  water,  and  in  briefest  outline  their  unique 
fitness  for  the  living  mechanism.  No  other 
known  substance  could  be  substituted  for 
water  as  the  material  out  of  which  oceans, 
lakes,  and  rivers  are  formed,  and  as  the  sub- 
stance which  passes  through  the  meteorolog- 
ical cycle,  without  radical  sacrifice  of  some 
of  the  most  vital  features  of  existing  condi- 
tions. Ammonia  in  these  respects  is  the  only 
substance  now  known  which  approaches  the 


110     THE   FITNESS  OF  THE  ENVIRONMENT 

fitness  of  water.  But  not  only  is  it  almost 
inconceivable  that  ammonia  should  ever  occur 
in  sufficiently  vast  quantities  upon  a  planet's 
surface,  but  it  is  evident  as  well  that  am- 
monia wholly  lacks  the  qualification  of  anoma- 
lous expansion,  and  also  in  some  of  the  most 
important  of  the  other  thermal  properties 
falls  far  short  of  water ;  -4^1e  in  latent  heat 
of  melting  and  in  specific  heat  its  advantage 
over  water  is  inconsiderable. 

It  is  obvious  that  upon  a  body  like  the 
earth  the  state  of  the  oceans  and  the  meteor- 
ological phenomena  are  of  the  utmost  impor- 
tance to  all  living  things.  Unless  these  be 
favorable,  human  experience  and  reflection 
alike  agree  that  life  could  not  widely  exist. 
It  seems,  therefore,  almost  safe  to  say,  on  the 
basis  of  its  thermal  properties  alone,  that 
water  is  the  one  fit  substance  for  its  place  in 
the  process  of  universal  evolution,  when  we 
regard  that  process  biocentrically. 


II 


THE    ACTION     OF    WATER    UPON    OTHER    SUB- 
STANCES 

Although  the  thermal  properties  of  water 
make  up  the  classical  subject-matter  for  dis- 
cussions   of    the    fitness   of    the    natural    en- 


WATER  111 

vironment,  other  no  less  important  physical 
properties  exist.  Such  especially  are  those 
characteristics  of  liquid  water  which  in  no 
small  measure  determine  the  nature  of  the 
resulting  physico-chemical  systems  when  other 
substances,  whether  soluble  or  insoluble,  crys- 
talline or  colloidal,  are  brought  into  contact 
with  it ;  I  mean  the  solvent  power,  the  dielec- 
tric constant,  together  with  the  related  ioniz- 
ing power,  and  the  surface  tension. 


WATER  AS  A  SOLVENT 

^^  As  a  solvent  there  is  literally  nothing  to 
compare  with  water.  In  truth  its  qualifi- 
cations are  on  this  point  so  unique  and  ob- 
vious that  nobody  seems  to  have  taken  the 
trouble  to  gather  together  the  evidence,  and, 
accordingly,  beyond  the  bare  assertion,  a  brief 
statement  of  the  facts  is  not  easy.^  In  the 
first  place  the  solubility  in  water  of  acids, 
bases,  and  salts,  the  most  familiar  classes  of 
inorganic  substances,  is  almost  universal. 

^  Nearly  the  whole  science  of  chemistry  has  been  built 
around  water  and  aqueous  solutions.  A  reference  to  any  text- 
book will  at  once  reveal  the  truth  of  this  statement.  At  first 
sight  such  a  condition  appears  to  be  a  matter  of  chance,  but, 
as  one  becomes  more  familiar  with  the  true  character  of  the 
science,  realization  of  a  rational  justification  for  the  historical 
fact  steadily  grows. 


112     THE  FITNESS  OF  THE  ENVIRONMENT 

Relatively  few  of  these  bodies  are  highly 
insoluble;  very  many  are  exceedingly  soluble 
in  water.  Apart  from  their  electrolytic  dis- 
sociation and  hydrolysis,  which  will  be  later 
discussed,  the  chemical  changes  wrought  upon 
such  dissolved  substances  in  solution  are 
commonly  very  unimportant.  For  chemical 
inertness,  depending  upon  great  stability, 
is  a  most  significant  characteristic  of  water, 
and  undoubtedly  a  highly  advantageous  one 
as  well. 

On  the  whole  the  best  evidence  for  the 
eflSciency  of  water  as  a  solvent  of  inorganic  sub- 
stances is  to  be  found  in  the  data  of  geology. 
Of  all  geological  agents  water  appears  to 
have  been  by  far  the  most  active  within  the 
periods  of  which  investigation  is  made  pos- 
sible by  the  geological  record.^  Rainfall, 
the  movement  of  surface  streams  and  of 
water  beneath  the  ground,  and  wave  action, 
all  contribute  to  the  work  of  disintegration, 
sedimentation,  etc.,  partly  by  dissolution  of 
soluble  material,  partly  by  mechanical  action. 
But  mechanical  action  is  itself  much  in- 
creased by  the  loosening  which  earlier  dis- 
solution has  caused.  In  this  manner  the  great 
solvent  power  of  water  throughout  its  meteor- 
ological cycle  largely  contributes  to  the  mobil- 

1  Geikie,  "Textbook  of  Geology,"  pp.  447-597. 


WATER  113 

ization  of  many  materials  which  could  not 
otherwise  be  brought  to  the  organisms  which 
need  them. 

It  has  been  calculated  by  Murray^  that 
the  total  yearly  run  off  of  all  the  rivers  of  the 
earth  is  about  6500  cubic  miles,  carrying 
nearly  5,000,000,000  tons  of  dissolved  mineral 
matter  and  prodigious  quantities  of  sediment. 
The  average  composition  of  such  water  has 
been   estimated   as  follows:  — 

Parts  per  Million 

Potassium  as  K2O 2.40 

Sodium  as  NazO .• 7.10 

Lithium  as  LiaO 0.20 

Calcium  as  CaO 43.20 

Magnesium  as  MgO 14.70 

Manganese  as  Mn304 1.20 

Iron  as  FeO        2.80 

Aluminium  as  AI2O3 3.10 

Silicon  as  SiOa 16.40 

Carbonic  acid  as  CO2 46 

Phosphorus  as  P2O5 0.30 

Nitric  acid  as  NsOs 3.80 

Sulphuric  acid  as  SO3 8 

Chlorine  as  CI 3.70 

Ammonia  as  NH3 0.07 

Total  mineral  matter 152.97 

It  is,  of  course,  almost  exclusively  to  these 
constant  accessions  that  the  ocean  owes  its 
salinity,  which  in  the  course  of  time  has 
reached  well-nigh  inconceivable  magnitude. 
The  common  salt  alone  in  the  oceans  of  all 

^  Russell,  "Rivers  of  North  America,"  p.  80. 
I 


114      THE  FITNESS  OF  THE  ENVIRONMENT 

the  earth  amounts  to  not  less  than  35,000,000,- 
000,000,000  tons.  Quite  as  significant  of  the 
solvent  power  of  water  is  the  variety  of 
elements  whose  presence  in  sea  water  can  be 
demonstrated,  thus  proving  that  the  total 
store  of  them  is  in  any  case  enormous.  They 
include  hydrogen,  oxygen,  nitrogen,  carbon, 
chlorine,  sodium,  magnesium,  sulphur,  phos- 
phorus, which  are  easily  demonstrated; 
further,  arsenic,  caesium,  gold,  lithium,  ru- 
bidium, barium,  lead,  boron,  fluorine,  iron, 
iodine,  bromine,  potassium,  cobalt,  copper, 
manganese,  nickel,  silver,  silicon,  zinc,  alumin- 
ium, calcium,  and  strontium.^ 

Equally  striking  is  the  evidence  in  regard 
to  the  first  stages  of  this  geological  process. 
Under  the  action  of  water,  aided,  to  be  sure, 
in  many  cases  by  dissolved  carbonic  acid, 
every  species  of  rock  suffers  slow  destruction. 
All  substances  yield  in  situ  to  the  solvent 
work  of  water,  and  the  dissolved  parts  may 
all  be  found  in  the  great  final  reservoir,  the 
ocean.  It  has  been  proved  that  nearly 
every  one  of  the  substances  which  are  thus 
set  in  motion  upon  the  face  of  the  earth  are 
placed  under  contribution  by  life,  for  bio- 
chemical analysis  reveals  them  as  constitu- 
ents   of     living    organisms,    absorbed    either 

^  Arrhenius,  "Kosmische  Physik." 


WATER  115 

on  their  way  down  from  the  mountain  tops 
to  the  ocean  or  by  the  marine  flora  and 
fauna. 

Not  less  valuable  to  the  community  of 
living  things  than  the  dissolution  of  the  rocks, 
is  the  disintegration  and  transport  of  solid 
material,  largely  dependent  thereon,  which 
among  its  many  results  includes  the  prelim- 
inary steps  of  soil  formation.  By  these 
familiar  and  enduring  geological  means  chemi- 
cal substances  are  mobilized  in  the  greatest 
variety  of  forms  and  conditions,  and  thus 
rendered  available  for  the  living  organism. 
It  is  clearly  evident  from  the  chemist's  long 
experience  with  solvents  that  no  other  fluid 
could  permanently  carry  on  this  process  with 
such  acceptable  regularity  and  efliciency. 
For  no  other  chemically  inert  solvent  can 
compare  with  water  in  the  number  of  things 
which  it  can  dissolve,  nor  in  the  amounts  of 
them  which  it  can  hold  in  solution ;  and  of 
course  any  chemically  active  solvent  must 
sooner  or  later  exhaust  itself  by  its  chemical 
action,  when  the  cycle  must  cease.  Here, 
then,  is  a  fitness  of  water  which  is  open  to  no 
doubt. 

Let  us  turn  for  further  proof  to  the  organ- 
isrri  itself,  taking  blood  serum  as  a  source  of 
information.     The    composition  of    this  sub- 


116      THE  FITNESS  OF  THE  ENVIRONMENT 

stance  (in  the  case  of  the  cow)  is  roughly  as 
follows :  ^  — 

Parts  per  1000 

Water        913.6 

Protein 72.5 

Sugar 1.05 

Cholesterine       1.24 

Lecithine        1.68 

Fat       0.93 

Organic  phosphoric  acid 0.01 

NazO 4.31 

K2O 0.26 

CaO 0.12 

MgO 0.45 

CI 3.69 

P2O6 0.08 

Most  of  these  substances  are  in  solution, 
and  unquestionably  a  host  of  others  are  pres- 
ent with  them,  in  small  and  varying  amounts. 
Among  these  may  be  mentioned  iodine, 
bromine,  iron,  sulphates,  urea,  ammonia,  ben- 
zoic acid,  amino-acids,  etc.  But  indeed  all 
substances  found  in  urine  (see  below)  also 
occur  in  blood.  It  cannot  be  doubted  that 
if  the  vehicle  of  the  blood  were  other  than 
water,  the  dissolved  substances  would  be 
greatly  restricted  in  variety  and  in  quantity, 
nor  that  such  restriction  must  needs  be  ac- 
companied by  a  corresponding  restriction  of 
the  life  processes. 

^  A  full  discussion  of  the  following  data  may  be  found  in 
such  works  as  those  of  Hammarsten  and  Abderhalden  on 
physiological  chemistry. 


WATER  117 

The  composition  of  the  jirine  provides 
another  excellent  illustration  of  the  utility 
of  the  solvent  power  of  water.  In  the  course 
of  its  complex  chemical  process^es  a  higher 
organism  produces  a  host  of  end  products 
which  must  be  removed,  and  also  finds  itself 
accidentally  in  possession  of  a  great  variety 
of  other  useless  substances  which  require 
excretion.  The  solvent  power  of  water  is 
one  of  the  great  factors  in  facilitating  this 
task.  Human  urine  has  been  reported  to 
contain  in  solution  the  following  substances: 
urea,  carbamic  acid,  creatinine,  creatine, 
uric  acid,  xanthine,  guanine,  hypoxanthine, 
adenine,  paraxanthine,  heteroxanthine,  epi- 
sarkine,  epiguanine,  oxalic  acid,  allantoine, 
hippuric  acid,  phenaceturic  acid,  benzoic  acid, 
phenolsulphuric  acid,  skatoxylsulphuric  acid, 
paraoxyphenylacetic  acid,  homogentisic  acid, 
urobiline,  urochrome,  uroerythrine,  glucose, 
levulose,  lactose,  numerous  compounds  of 
glycuronic  acid,  glycine,  alanine,  leucine,  tyro- 
sine, and  other  amino-acids,  various  enzymes, 
putrescine,  cadavarine,  and  countless  other 
organic  substances,  chlorides,  bromides,  and 
iodides,  phosphates  and  sulphates,  potassium, 
sodium,  ammonia,  calcium,  magnesium,  iron, 
carbonic  acid,   nitrogen,   argon,   etc. 

Here  again  it  is  sure  that  such  variety  could 


118     THE  FITNESS  OF  THE  ENVIRONMENT 

not  be  attained  with  another  solvent.  It  is 
no  exaggeration  to  say  that  except  atmos- 
pheric oxygen  and  carbonic  acid,  nearly  all 
the  food  of  living  organisms  is  water  borne, 
and  all  material  in  its  passage  into  the  body, 
through  the  body,  and  out  of  the  body  nearly 
always  employs  the  same  vehicle.  Cer- 
tainly no  other  form  of  transport  would  be  so 
efficient  and  so  economical. 

B 

IONIZATION 

If,  therefore,  aqueous  solutions  are,  ap- 
parently of  necessity,  the  very  basis  of  the 
life  processes,  the  state  of  substances  when  in 
this  condition,  and  also  when  in  contact  with 
water,  is  of  vital  importance.  Here  two  prop- 
erties of  water,  the  dielectric  constant  and 
the  surface  tension,  exert  a  cardinal  influence. 

Among  the  phenomena  of  solution  those 
which  are  related  to  electrolytic  dissociation, 
as  suggested  by  the  hypothesis  of  Arrhenius, 
have  deservedly  received  a  great  deal  of  at- 
tention since  the  secure  establishment  of  the 
new  science  of  physical  chemistry  in  the 
eighties  of  the  last  century.  In  the  course 
of  time  the  belief  that  in  aqueous  solution 
the  molecules  of  all  acids,  bases,  and  salts 
are  more  or  less  split  into  particles  which  bear 


WATER  119 

electrical  charges  has  been  universally  ac- 
cepted. These  so-called  ions  are  the  source 
of  nearly  all  the  electrical  phenomena  of  solu- 
tion, whether  in  batteries,  in  the  manifesta- 
tions of  animal  electricity,  or  in  simple  con- 
duction through  an  aqueous  solution.  But 
the  more  familiar  electrochemical  processes 
are  by  no  means  the  only  results  of  ioniza- 
tion. An  infinite  number  of  chemical  inter- 
actions between  dissociated  bodies  follow 
inevitably.  These  changes  are  not,  to  be 
sure,  decisive  and  irreversible,  but  balanced 
actions,  which,  however,  vastly  increase  the 
variety  of  substances  that  exist  in  water. 

Let  us  consider,  for  example,  a  system  which 
has  been  made  by  dissolving  in  water  the 
simple  salts  sodium  chloride,  NaCl,  potas- 
sium bromide,  KBr,  and  lithium  iodide,  Lil. 
According  to  the  ionization  hypothesis,  more 
than  half  of  the  molecules  of  every  one  of 
these  salts  will  at  once  dissociate  into  ions  as 
follows :  — 

NaCl  =  Na  +  Cl 

KBr  =  K  +  Br 

LiI  =  Li  +  i 

These  reactions  are  balanced,  and  it  is 
confidently   believed   that  the   ions   are   con- 


120     THE  FITNESS  OF  THE  ENVIRONMENT 

stantly  recombining  to  form  molecules  and 
the  molecules  constantly  dissociating  once 
more  to  form  ions.  At  the  same  time,  noth- 
ing hinders  the  union  of  sodium  ions  with 
bromine  ions,  or  of  any  other  pair  of  positive 
and  negative  ions.  Accordingly,  the  solu- 
tion at  once  contains  not  only  the  three  origi- 
nal salts  and  the  six  different  varieties  of 
ions,  but  also  the  following  new  molecules :  — 
sodium  bromide,  NaBr,  sodium  iodide,  Nal, 
potassium  chloride,  KCl,  potassium  iodide,  KI, 
lithium  chloride,  LiCl,  and  lithium  bromide, 
LiBr.  All  nine  varieties  of  molecules  and 
all  six  of  ions  are  concerned  in  a  complicated 
system  of  chemical  reactions  which  are  now 
well  understood,  the  state  of  equilibrium 
depending  upon  known  conditions.  For  in- 
stance, if  the  solution  be  a  moderately  dilute 
one  and  the  original  substances  be  present  in 
chemically  equivalent  quantities,  about  90 
per  cent  of  the  material  will  be  in  the  ionic 
state,  each  variety  of  ions  making  up  about  15 
per  cent  of  the  total,  and  about  10  per  cent 
will  be  in  the  form  of  molecules,  each  variety 
constituting  about  1.1  per  cent. 

There  can  be  no  doubt  that  ionization 
plays  a  great  part  in  determining  the  char- 
acteristics of  solutions  of  acids,  bases,  and 
salts,  and  in  bringing  about  the  reactions  which 


WATER  121 

occur  among  them,  and  between  them  and 
other  substances. 

Such,  then,  is  the  process  to  which  are  due 
most  of  the  electrical  phenomena  and  many 
of  the  chemical  phenomena  of  solutions,  and 
it  is  certain  that  the  extent  and  variety  of 
ionization  in  water  far  surpass  what  is  possi- 
ble in  any  other  solvent.  One  reason  for  this 
is  most  simple.  The  ionizing  substances  are 
so  very  much  more  often  soluble  in  water 
than  in  any  other  solvent,  and  when  soluble 
are  in  general  so  much  more  highly  soluble, 
that  the  opportunity  for  ionization  in  water 
is  quite  unparalleled.  Further,  ionization  in 
solution  unquestionably  depends  upon  the 
dielectric  constant  of  the  solvent,  in  accord- 
ance with  the  principle  first  stated  by  Nernst 
that  the  greater  the  dielectric  capacity  of  the 
solvent,  the  greater  is  the  degree  of  electro- 
lytic dissociation  of  substances  dissolved  in  it, 
when  the  conditions  are  otherwise  the  same.^ 

^  "The  following  consideration  will  make  this  principle 
clearer :  The  positively  and  negatively  charged  ions  would 
unite  to  form  electrically  neutral  molecules  because  of  the 
electrostatic  attraction  which  exists  between  them  if  it  were 
not  for  the  action  of  another  and  opposing  force,  the  nature  of 
which  is  as  yet  unknown.  The  equilibrium  between  these 
two  forces  gives  rise  to  the  equilibrium  between  the  ions  and 
the  undissociated  molecules,  or  determines  the  degree  of  dis- 
sociation.    When   the   dielectric   constant   is   increased,    the 


122     THE  FITNESS  OF  THE  ENVIRONMENT 

This  is  the  case  because  the  tendency  of  the 
electrically  charged  ions  to  reunite  and  form 
electrically  neutral  molecules  must  be  less 
the  greater  the  dielectric  constant  of  the  sol- 
vent. Now  the  dielectric  constant  of  water 
is  nearly  the  highest  at  present  known,  and 
therefore  ionization  in  water  is  on  that  account 
also  more  extensive  than  in  almost  any  other 
solvent. 

Finally,  for  reasons  that  are  not  yet  under- 
stood, the  process  of  ionization  in  other  sol- 
vents than  water  is  a  much  more  complex 
affair,  and  there  can  be  no  doubt  that  such 
complexity  limits  the  phenomena  which  are 
dependent  upon  ionization.^ 

electrostatic  attraction  between  the  ions  is  alone  weakened, 
and  hence  the  degree  of  dissociation  is  increased."  —  Lb 
Blanc,  "A  Textbook  of  Electro-Chemistry."  New  York, 
1907,  p.  147. 

^  "It  would  be  natural  to  expect  that  the  conceptions 
which  have  been  found  serviceable  in  the  case  of  solutions  in 
water  could  be  applied  directly  to  solutions  in  other  solvents, 
keeping  in  mind  that,  according  to  the  individual  nature  of 
any  given  solvent,  the  degree  of  dissociation,  the  migration 
velocity  of  the  ions,  and  consequently  the  conductivity  of  a 
solution  of  a  given  concentration  would  be  different.  It  is 
a  noteworthy  fact,  however,  that  the  behavior  of  non-aque- 
ous is  much  more  complicated  than  that  of  aqueous  solutions. 
This  is  shown  especially  by  the  investigation  of  the  conduc- 
tivity of  solutions  of  various  substances  in  liquid  sulfur  dioxide 
made  by  Walden  and  Centnerszwer.  Neither  the  law  of  the 
independent  migration  of  the  ions,  nor  the  law  that  by  increas- 


WATER  123 

Physiologically,  as  researches  of  the  last 
twenty  years  clearly  prove,  the  action  of  ions 
is  of  fundamental  significance.  The  brilliant 
investigations  of  J.  Loeb,  and  the  long  series 
of  studies  by  various  other  physiologists  of 
the  influence  of  electrolytes  upon  colloids 
form  perhaps  the  most  telling  evidence  for 
this  belief.^  At  all  events  there  is  no  ques- 
tion that  the  simple  equilibria  between  acids 
and  bases  and  salts  are  of  extreme  importance 
in  physiological  processes.  They  lie  at  the 
very  basis  of  the  structure  of  all  protoplasm, 

ing  dilution  the  conductance  approaches  a  maximum  value, 
nor,  finally,  the  dilution  law,  was  found  to  hold.  Molecular 
weight  determinations  carried  out  at  the  same  time  by  the 
boiling-point  method  gave  normal  values  for  non-electrolytes, 
and  abnormally  large  values  for  electrolytes,  whereas  abnor- 
mally small  values  would  be  expected.  This  indicates  that 
association  has  taken  place,  to  a  considerable  extent,  which 
in  all  probability  takes  place  not  only  between  molecules  of 
dissolved  substance,  but  also  between  these  molecules  and 
those  of  the  solvent.  Considering  these  circumstances,  it 
is  very  fortunate  for  the  advance  of  the  sciences  of  chemistry 
and  electro-chemistry  that  such  complications  are  generally* 
although  not  always,  absent  in  the  case  of  aqueous  solutions. 
It  is  due  to  this  fact  that  it  has  been  possible  to  deduce  simple 
laws  from  a  study  of  such  solutions."  —  Le  Blanc,  "A  Text- 
book of  Electro-Chemistry."  New  York,  1907,  pp.  142-143. 
1  Full  discussion  of  such  subjects  will  be  found  in  the 
"Dynamics  of  Living  Matter,"  by  Loeb,  and  in  his  contribu- 
tion to  Oppenheimer's  "Handbuch  der  Biochemie,"  as  well 
as  in  Hober's  "  Physikalische  Chemie  der  Zelle  und  der 
Gewebe." 


124     THE   FITNESS  OF  THE  ENVIRONMENT 

and  the  sure  and  definite  relations  between 
such  bodies  provide,  as  it  were,  a  secure  foun- 
dation for  the  more  complex  organic  structures. 

More  obvious  is  the  value  of  ions  as  sources 
of  electricity.  If  the  older  electro-physiology 
of  the  third  quarter  of  the  nineteenth  cen- 
tury has  proved  in  some  respects  a  sterile 
field,  there  can  yet  be  no  doubt  that  more 
subtly,  and  quite  apart  from  the  nervous  im- 
pulse and  the  peculiar  phenomena  of  electrical 
fishes,  electrical  phenomena  are  everywhere 
involved  in  the  most  intimate  of  the  physio- 
logical processes. 

Even  without  further  discussion  of  a  sub- 
ject that  must  soon  lead  into  difficult  and 
highly  technical  considerations,  I  feel  sure 
that  the  existence  of  another  important  fitness 
of  water  is  patent.  For  ions  are  evidently 
a  real  contribution  to  the  richness  of  the 
environment.  They  enhance  the  variety  of 
chemical  substances  and  of  chemical  reactions  ; 
they  constitute  a  group  of  singularly  mobile 
chemical  agents ;  they  provide  electricity ; 
and,  finally,  aqueous  solutions  are  by  far  the 
best  source  of  ions. 

It  must  be  pointed  out  before  leaving  this 
subject  that  the  dielectric  constant,  hence 
the  ionizing  power,  is  somehow  related  to 
various  other  properties  of  the  solvent.     In 


WATER 


125 


the  accompanying  table  Kd  stands  for  the 
dielectric  constant,  Hy  for  the  latent  heat 
of  vaporization,  and  Kh  for  the  absolute 
conductivity  for  heat.  It  is  to  be  observed 
that  on  the  whole  all  three  quantities  decrease 
simultaneously.  These  properties  are  also 
related  to  the  critical  pressure,  to  the  van 
der  Waals  constant  a,  and  to  the  molecular 
volume  at  the  boiling  point. 


Solvent 


Kd 

Hy 

81.7 

536.5 

32.5 

267.5 

21.7 

205 

57.0 

103.7 

6.5 

89.8 

16 

329 

<10.5 

14 

92.5 

20.7 

125.3 

5.85 

86.7 

2.26 

93.5 

2.31 

83.6 

4.36 

84.5 

4.95 

58.5 

2.18 

46.35 

3.2 

30.53 

Water,  H2O 

Methyl  alcohol,  CH3OH  .  .  . 
Ethyl  alcohol,  C2H5OH  .  .  . 
Formic  acid,  H  •  COOH  .  .  . 
Acetic  acid,  CH3  •  COOH      .     . 

Ammonia,  NH3 

Methylamine,  CH3  •  NH2  .  . 
Sulphurous  oxide,  SO2  .  •  . 
Acetone,  CH3  •  CO  •  CH3  .  .  . 
Ethylacetate,  CH3  •  CO  •  O  •  C2H5 

Benzene,  CeHe 

Toluene,  CeHs  •  CH3    .... 

Ether,  (C2H.5)20 

Chloroform,  CHCI3  .... 
Tetrachlorraethane,  CCI4  .  . 
Stannic  chloride,  SnCU     .     .     . 


0.154 

0.0495 

0.0423 

0.0648 

0.0472 


0.0348 
0.0333 
0.0307 
0.0303 
0.0288 
0.0252 


Such  evidence  clearly  suggests  that  some 
of  the  manifold  fitnesses  of  water  proceed 
from  a  single  cause  or  group  of  causes.  For 
the  present,  however,  these  relationships  are 


126      THE   FITNESS  OF  THE  ENVIRONMENT 

obscure,  and  in  any  case  there  seems  to  be 
no  immediate  hope  of  bringing  them  into 
connection  with  the  science  of  biology. 

C 

SURFACE  TENSION 

Of    all    common    liquids,    except    mercury, 
water  has  the  greatest  surface  tension. 

Table  of  Surface  Tensions 

Water 75 

Carbonic  acid 1.8 

Ammonia 41.8 

Mercury       436 

Benzene        28.8 

Methyl  alcohol 23 

Ethyl  alcohol    .     .     .  ^ 22 

Ether 16.5 

Glycerine 65 

Acetone 23 

Formic  acid 37.1 

Acetic  acid        23.5 

Chloroform       26 

This  fact  is  of  enormous  moment  in  biology, 
most  obviously  perhaps  in  its  influence  upon 
the  soil.  For  surface  tension  and  density 
determine  the  height  to  which  a  liquid  will 
rise  in  a  capillary  system,  and  thus  it  comes 
about  that  the  principal  factor  in  bringing 
water  within  reach  of  plants  is  the  exceptional 
surface  tension  of  water.  The  nature  of  the 
case  is  clearly  explained  by  Hilgard.     "The 


WATER  127 

liquid  water  held  in  the  pores  of  the  soil,  in 
the  form  of  surface  films  representing  the 
curved  surface  seen  in  capillary  tubes,  and 
therefore  tending  to  cause  the  water  to  move 
upwards,  as  well  as  in  all  other  directions, 
until  uniformity  of  tension  is  established,  is 
of  vastly  higher  importance  to  plant  growth 
than  hygroscopic  moisture.  It  not  only  serves 
normally  as  the  vehicle  of  all  plant  food  ab- 
sorbed during  the  growth  of  the  usual  crops, 
but  also,  as  a  rule,  to  sustain  the  enormous 
evaporation  by  which  the  plant  maintains, 
during  the  heat  of  the  day,  a  temperature 
sufficiently  low  to  permit  of  the  proper  op- 
eration of  the  processes  of  assimilation  and 
building  of  cell  tissue."  ^ 

The  rise  of  w^ater  in  capillary  systems  re- 
sembling soil,  under  the  action  of  surface 
tension,  may  be  as  much  as  ten  feet.  In  soil 
itself  the  highest  rise  under  the  usual  circum- 
stances is  unquestionably  as  much  as  four 
or  five  feet;  but  if  the  surface  tension  of 
water  were  like  that  of  most  liquids  it  could 
be,  under  similar  conditions,  but  two  or  three 
feet.  There  seems  to  be  little  doubt  that  the 
rise  of  fluids  in  tall  plants  is  also  in  large 
part  due  to  the  action  of  surface  tension,  and 
accordingly  it  must  be  much  favored  by  the 

1  Hilgard,  "Soils."     New  York,  1907,  p.  201. 


7 


128     THE  FITNESS  OF  THE  ENVIRONMENT 

magnitude  of  that   quantity  in   the  case   of 
water. 

Finally,  surface  tension  is  of  great  impor- 
tance, indeed  in  simple  cases  is  the  one  effective 
agent,  in  the  phenomenon  called  adsorption.^ 
On  the  basis  of  thermodynamical  considera- 
tions first  developed  by  Willard  Gibbs,  it  is 
easy  to  show  that  whenever  the  dissolution 
of  a  substance  changes  the  surface  tension 
of  a  solvent,  the  distribution  of  the  dis- 
solved substance  will  not  be  strictly  homo- 
geneous. If  the  solution  has  a  lower  surface 
tension  than  the  ^olvent^the  surface  of  the 
solution  will  become  more  concentrated  than 
the  interior ;  or  if  the  surface  tension  of  the 
solution  be  greater  than  that  of  the  solvent, 
the  surface  of  the  solution  will  become  less 
concentrated  than  the  interior.  This  result, 
quite  insignificant  in  simple  solutions,  becomes 
a  matter  of  much  moment  when,  as  in  the 
case  of  suspensions  of  fine  particles  like  ani- 
mal charcoal,  in  emulsions,  jellies,  or  any 
other  system  of  like  disperse  heterogeneity 
of  physical  constitution,  there  occurs  very 
great   increase   of   surface   area.     Then   it   is 

^  A  familiar  example  of  adsorption  is  the  use  of  bone- 
black  to  decolorize  sirup  in  the  process  of  sugar  refining. 
The  colored  matters  are  almost  completely  removed  from 
solution,  and  cling  to  the  surface  of  the  charcoal. 


WATER  129 

that  adsorption  becomes  a  factor  of  the  great- 
est weight;  for,  other  things  being  equal, 
the  total  force  of  surface  tension  in  a  system 
is  proportional  to  the  area  of  surface.  Under 
these  circumstances  dissolved  substances  are 
no  longer  distributed  with  any  approach  to 
equality  or  regularity  in  the  system,  but  they 
collect  at  the  surface  in  very  great  quantities, 
and  in  the  most  irregular  manner. 

Now  of  all  known  physical  structures  there 
is  none  which  rivals  protoplasm  in  its  fine 
complexity,  and  adsorption  is  therefore  un- 
questionably a  prominent  agent  in  deciding 
its  physico-chemical  constitution.  Moreover, 
adsorption  influences  and  complicates  almost 
every  process  of  chemical  physiology,  for  no 
product  of  life  is  without  its  colloids,  i.e.  sub- 
stances which  are  finely  divided  and  there- 
fore endowed  with  great  surface  areas.  In 
truth  colloids  are  probably  quite  essential  to 
fine  complexity,  and  so  to  every  conceivable 
form  of  life.^ 

The  evidence  for  this  universal  importance 

^  "Eines  aber  mochte  ich  behaupten,  welches  auch  immer 
die  stoffliche  Zusammensetzung  jener  Lebewesen  (living 
organisms  in  another  world)  sein  mag :  es  miissen  Kolloide 
sein.  .  .  .  Welcher  andere  Zustand,  ausser  dem  KoUoiden, 
konnte  derart  veranderliche,  derart  plastische  Formen  bilden 
und  ware  doch  im  stande,  diese  Formen,  wenn  notig,  unver- 
anderlich  zu  wahren."  —  Bechhold,  I.e.,  p.  194. 


130     THE  FITNESS  OF  THE  ENVIRONMENT 

of  adsorption  in  biology  is  not  to  be  briefly 
presented,  but  it  may  be  found  in  almost 
endless  profusion  in  such  works  as  those  of 
Freundlich  and  Bechhold.^ 

It  must  not  be  supposed  that  the  phenomena 
of  adsorption  in  biology  are  simple  and  exactly 
understood.  What  is  certain  is  that  they 
are  universal,  and  that  surface  tension  lies 
at  the  root  of  the  matter.  This  is  because 
all  living  things  are  colloidal,  and  I  am  in- 
clined to  think  that  most  physiologists  will 
admit  that  life  without  colloids  is  probably 
unthinkable,  even  in  a  world  very  differently 
constituted  from  our  own.  Colloidal  struc- 
tures are,  in  fact,  the  first  and  greatest  factors 
in  physical  complexity  of  organization,  and 
the  principal  force,  unless  it  be  in  exceptional 
cases  an  electrical  charge  due  to  ions,  which 
operates  upon  the  colloidal  structures  is  sur- 
face tension.  This,  then,  is  another  striking 
fitness  of  water  above  all  other  things. 

Such  are  the  facts  which  I  have  been  able 
to  discover  regarding  the  fitness  of  water  for 
the  organism.  The  following  properties  ap- 
pear  to   be   extraordinarily,    often   uniquely, 

^  Freundlich,  "Kapillarchemie."  Leipzig,  1909.  Bech- 
hold,  "Die  Kolloide  in  Biologie  und  Medizin."  Dresden, 
1911. 


WATER  131 

suited  to  a  mechanism  which  must  be  complex, 
durable,  and  dependent  upon  a  constant 
metabolism :  heat  capacity,  heat  conductiv- 
ity, expansion  on  cooling  near  the  freezing 
point,  density  of  ice,  heat  of  fusion,  heat  of 
vaporization,  vapor  tension,  freezing  point, 
solvent  power,  dielectric  constant  and  ionizing 
power,  and  surface  tension.^ 

In  no  case  do  the  advantages  which  these 
properties  confer  seem  to  be  trivial ;  com- 
monly they  are  of  the  greatest  moment; 
and  I  cannot  doubt,  even  after  allowances 
have  been  made  for  the  probability  of  occa- 
sional fallacies  in  the  development  of  an  argu- 
ment which,  though  simple,  is  beset  with  many 
pitfalls,  that  they  are  decisive.  Water,  of  its 
very  nature,  as  it  occurs  automatically  in  the 
process  of  cosmic  evolution,  is  fit,  with  a  fitness 
no  less  marvelous  and  varied  than  that  fitness 
of  the  organism  which  has  been  won  by  the 
process  of  adaptation  in  the  course  of  organic 
evolution. 

If  doubts  remain,  let  a  search  be  made  for 

^  Contrasting  this  statement  with  that  of  Whewell  in  his 
Bridgewater  Treatise,  it  is  evident  that  while  the  progress 
of  science  has  provided  much  novel  information,  and  elim- 
inated many  false  views,  the  present  situation  differs  from  the 
earlier  one  only  in  the  better  definition  of  the  issue,  and  in 
our  modern  freedom  from  metaphysical  and  theological 
associations. 


132     THE  FITNESS  OF  THE  ENVIRONMENT 

any  other  substance  which,  however  shghtly, 
can  claim  to  rival  water  as  the  milieu  ^  of 
simple  organisms,  as  the  milieu  interieur  of 
all  living  things,  or  in  any  other  of  the  count- 
less physiological  functions  which  it  performs 
either  automatically  or  as  a  result  of  adapta- 
tion. 

In  truth  Darwinian  fitness  is  a  perfectly 
reciprocal  relationship.  In  the  world  of 
modern  science  a  fit  organism  inhabits  a  fit 
environment. 

1  Here  and  elsewhere  the  word  ** milieu"  has  been  employed 
when  it  is  desired  to  express  only  that  part  of  the  conception 
of  environment  which  is  involved  in  the  literal  meaning  of 
the  word,  leaving  to  environment  the  added  significance  of 
that  which  provides  food. 


CHAPTER  IV 
CARBONIC  ACID 

TWO  chemical  individuals  stand  alone  in 
importance  for  the  great  biological 
cycle  upon  the  earth.  The  one  is  water,  the 
other  carbon  dioxide.  The  one,  for  reasons 
which  we  have  just  reviewed,  is  the  most 
familiar  of  all  the  varieties  of  matter.  The 
other  rarely  is  seen  except  by  chance,  and  with- 
out scientific  research  never  could  have  been 
known  for  what  it  is  in  value  to  living  things. 
Yet  these  two  simple  substances  are  the  com- 
mon source  of  every  one  of  the  complicated 
substances  which  are  produced  by  living 
beings,  and  they  are  the  common  end  prod- 
ucts of  the  wearing  away  of  all  the  constitu- 
ents of  protoplasm,  and  of  the  destruction  of 
those  materials  which  yield  energy  to  the 
body.^ 

^  A  man  weighing  60-70  kilograms  excretes  daily  the  fol- 
lowing quantities  of  material :  — 

Water 2500-3500  grams 

Carbon  dioxide    ....  750-900  grams 

All  other  substances     .     .  60-125  grams 

133 


134    THE  FITNESS  OF  THE  ENVIRONMENT 

Once  perhaps  the  atmosphere  of  the  earth 
consisted  chiefly  of  water  and  carbon  dioxide; 
but  cooHng  has  caused  the  condensation  of 
most  of  the  water,  and  geological  processes, 
more  recently  aided  by  the  action  of  vegetation 
with  coal  and  peat  formation,  have  removed 
nearly  all  of  the  carbon  dioxide.  The  latter 
transformations  have  resulted  in  the  substitu- 
tion of  oxygen  in  the  atmosphere.  However, 
the  interior  of  the  earth  continues  to  deliver 
through  volcanoes  large  amounts  of  carbon 
dioxide,  and  thus  the  original  source  of  atmos- 
pheric carbon  dioxide  persists  as  a  diminish- 
ing supply. 

To-day  carbon  dioxide  makes  up  only  a 
little  more  than  0.03  per  cent  by  volume  of 
the  whole  atmosphere,  approximately  4.6 
kilograms  per  square  meter  of  the  earth's 
surface,    or    about    2,300,000,000,000    metric 

Water  is,  therefore,  three  fourths,  carbon  dioxide  one  fifth, 
of  the  total,  and  all  other  substances  amount  to  but  2  to  3 
per  cent. 

In  like  manner  the  materials  ingested  by  an  ordinary  green 
plant  are  proportioned,  water  making  up  more  than  nine 
tenths,  and  carbon  dioxide  amounting  to  fully  five  times  the 
sum  of  all  other  substances  combined. 

Needless  to  say,  a  large  part  of  the  water  which  enters 
and  leaves  plants  and  animals  has  had  no  real  share  in  their 
organization.  It  is  merely  the  bearer  of  dissolved  substances 
or  the  means,  through  evaporation,  of  lowering  the  tempera- 
ture of  their  bodies. 


CARBONIC   ACID 


135 


tons  for  the  whole  earth. ^  In  the  ocean  the 
amount  of  carbonic  acid  is  about  0.1  gram  per 
Hter,  or  approximately  0.01  per  cent  by 
weight.  Here,  however,  much  the  larger 
part  is  in  chemical  union  with  bases,  chiefly 
in  the  form  of  bicarbonates.^ 

There  can  be  no  doubt  that  the  physical 
properties  of  carbon  dioxide  are  less  important 
to  the  living  organism  than  are  those  of  water. 
But  indeed  the  characteristics  of  water  so 
largely  determine  the  nature  of  the  environ- 

^  The  composition  of  dry  air  is  as  follows  :  — 


Nitrogen  .  . 
Oxygen  .  . 
Argon  .  .  . 
Carbon  dioxide 


Per  Cubic  Meter 


Volume  in  Liters 


Weight  in 
Grams 


Per  Kilogram 


2  See  below  in  the  discussion  of  the  alkalinity  of  the  ocean. 


136     THE  FITNESS  OF  THE  ENVIRONMENT 

ment  and  the  conditions  within  the  organism 
alike,  that  this  is  necessarily  the  case.  How- 
ever, the  less  conspicuous  substance  is  not 
without  its  physical  fitnesses,  and  we  must 
now  turn  to  them. 


SOLUBILITY 

The  most  obvious  of  the  properties  of  car- 
bonic acid  is  its  all-pervasiveness.  Originally 
formed  in  vast  quantities  by  the  cosmic  pro- 
cess, and  accumulated  in  the  atmosphere,  the 
store  has  been  steadily  replenished  there  by 
vulcanism.  It  is  probable  that  of  the  enor- 
mous quantities  now  deposited  as  limestone 
in  the  earth's  crust,  a  quantity  sufficient  to 
yield  an  atmospheric  pressure  greater  ten- 
fold than  the  present  atmospheric  pressure, 
only  a  fraction  was  at  any  one  time  actually 
gaseous.  For  it  happens  that  the  presence 
of  carbonic  acid  in  the  atmosphere  insures  the 
occurrence  of  greater,  or  at  least  nearly  equal, 
quantities  in  the  ocean  and  in  all  the  natural 
waters  of  the  earth.  This  is  due  to  the  solu- 
bility of  carbon  dioxide,  to  the  magnitude  of 
its  absorption  coefficient  in  water. 

The  absorption  coefficient  is  the  volume 
of  gas  absorbed  by  one  liter  of  liquid  when 


CARBONIC  ACID  137 

the  gas  pressure  is  one  atmosphere.  Accord- 
ing to  the  law  of  Henry,  however,  the  absorp- 
tion of  the  gas  is  always  proportional  to  its 

Table  of  Absorption  Coefficients  at  0° 

Oxygen 0.049 

Hydrogen 0.021 

Nitrogen 0.024 

Carbon  monoxide 0.035 

Carbon  dioxide 1.797 

Sulphurous  oxide 79.79 

Ammonia 1299 

partial  pressure  in  the  atmosphere,  and  there- 
fore the  absorption  coefficient  measures  the 
ratio,  after  equilibrium  has  been  attained, 
between  the  concentration  of  a  substance  in 
solution  and  in  the  gaseous  state,  no  matter 
what  that  concentration  may  be. 

The  absorption  coefficient  is  not  constant 
under  all  circumstances,  and  varies  especially 
with  the  temperature. 

Table  of  Absorption  Coefficients  of  CO2 

Temperatuhe  Absorption  Coefficient 

0°  1.797 

10°  1.185 

20"  0.901 

37.29°  0.563 

100°  0.244 

It  will  be  seen  from  the  tables  that,  differ- 
ing from  most  gases,  carbon  dioxide  has  an 
absorption  coefficient  nearly  equal  to  one,  and 


138     THE   FITNESS  OF  THE  ENVIRONMENT 

that  for  the  ordinary  temperature  of  the  earth's 
waters,  where  they  are  in  contact  with  car- 
bonic acid  gas,  it  is  very  close  indeed  to  1.0. 
Hence,  when  water  is  in  contact  with  air,  and 
equihbrium  has  been  estabhshed,  the  amount 
of  free  carbonic  acid  in  the  water  is  almost 
exactly  equal  to  the  amount  in  the  air.  Unlike 
oxj^gen,  hydrogen,  and  nitrogen,  carbonic  acid 
enters  water  freely ;  unlike  sulphurous  oxide 
and  ammonia,  it  escapes  freely  from  water. 
Thus  the  waters  can  never  wash  carbonic  acid 
out  of  the  air,  nor  the  air  keep  it  from  the 
waters.  It  is  the  one  substance  which  thus, 
in  considerable  quantities  relative  to  its  total 
amount,  everywhere  accompanies  water. ^  In 
earth,  air,  fire,  and  water  alike  these  two  sub- 
stances are  always  associated. 

Accordingly,  if  water  be  the  first  primary 
constituent  of  the  environment,  carbonic  acid 
is  inevitably  the  second,  —  because  of  its 
solubility  possessing  an  equal  mobility  with 
water,  because  of  the  reservoir  of  the  at- 
mosphere never  to  be  depleted  by  chemical 

1  "Carbonic  acid  being  more  soluble  than  the  other  gases, 
is  contained  in  rain  water  in  proportions  between  30  and  40 
times  greater  than  in  the  atmosphere."  —  Geikie,  "Text- 
book of  Geology."     4th  ed.,  Vol.  I,  p.  449,  1903. 

It  must  not  be  forgotten  that  carbonic  acid  in  subterranean 
water,  by  which  so  much  geological  change  is  accomplished, 
originates,  not  in  the  air,  but  from  organic  matter  in  the  soil. 


CARBONIC   ACID  139 

action  in  the  oceans,  lakes,  and  streams.  In 
truth,  so  close  is  the  association  between  these 
two  substances  that  it  is  scarcely  correct  logi- 
cally to  separate  them  at  all ;  together  they 
make  up  the  real  environment  and  they  never 
part  company.  Carbonic  acid  thus  possesses 
the  first  great  qualification  of  a  food:  its 
occurrence  is  universal  and  its  mobility  a 
maximum.  This  is  due  to  the  fact  that  its 
absorption  coefficient  is  on  the  average  ap- 
proximately one,  the  most  favorable  value. 

Needless  to  say  the  absorption  coefficient 
of  carbonic  acid  is  also  of  great  importance 
in  many  physiological  processes,  chiefly  per- 
haps in  excretion.  In  the  course  of  a  day  a 
man  of  average  size  produces,  as  a  result  of 
his  active  metabolism,  nearly  two  pounds  of 
carbon  dioxide.  All  this  must  be  rapidly  re- 
moved from  the  bod^^  It  is  difficult  to  im- 
agine by  what  elaborate  chemical  and  physical 
devices  the  body  could  rid  itself  of  such  enor- 
mous quantities  of  material  were  it  not  for 
the  fact  that,  in  the  blood,  the  acid  can  cir- 
culate partly  free  ^  and,  in  the  lungs,  by  a  pro- 
cess which  under  ordinary  circumstances  has 
all  the  appearances  of  a  simple  physical  phe- 

^  Of  the  total  carbonic  acid  of  the  blood  5-10  per  cent 
exists  as  the  free  acid,  partly  in  the  plasma,  partly  in  the  cor- 
puscles. 


140    THE  FITNESS  OF  THE  ENVIRONMENT 

nomenon,^  can  escape  into  air  which  is  charged 
with  but  httle  of  the  gas.^  Were  carbon 
dioxide  not  gaseous,  its  excretion  would  be 
the  greatest  of  physiological  tasks ;  were  it 
not  freely  soluble,  a  host  of  the  most  universal 
existing  physiological  processes  would  be  im- 
possible. 

n 

ACIDITY 

The  only  other  property  of  this  substance 
which  calls  for  consideration  at  this  point  is 
its  acid  nature  and  strength.  Very  few  min- 
erals are  freely  soluble  in  pure  water,  and 
nearly  all  yield  to  the  process  of  weathering 
far  more  readily  because  of  the  carbonic  acid 
which  all  natural  waters  contain.^     The  latter 

^  The  determination  of  the  exact  nature  of  the  process 
by  which  carbonic  acid  is  excreted  across  the  lung  membrane 
is  one  of  the  standing  difficulties  of  physiology,  but  we  need 
not  here  enter  upon  its  consideration. 

2  Expired  air  contains  on  the  average  more  than  4  per  cent 
by  volume  of  carbonic  acid. 

3  "A  few  minerals  (halite,  for  example)  are  readily  soluble 
in  water  without  chemical  change,  and  without  the  aid  of  any 
intermediate  element;  hence  the  copious  brine-springs  of 
salt  regions.  In  the  great  majority  of  cases,  however,  solu- 
tion is  effected  through  the  medium  of  carbonic  acid  or  other 
reagent.  Limestone  is  soluble  to  the  extent  of  about  1  part 
in  1000  of  water  saturated  with  carbonic  acid.  The  solution 
and  removal  of  Ume  from  the  mortar  of  a  bridge  or  vault. 


CARBONIC  ACID  141 

constituent  is  probably  a  necessary  adjuvant 
in  the  most  far-reaching  geological  phenom- 
ena. Indeed,  it  is  the  united  action  of  water 
and  carbonic  acid,  aided  in  lesser  degree  by 
nitric  acid,  which  has  been  formed  in  the  atmos- 
phere by  electrical  action,  and  by  acid  prod- 
ucts of  vegetation,  which  sets  free  the  in- 
organic constituents  of  the  earth's  crust  and 
turns  them  into  the  stream  of  metabolism. 

But  apart  from  the  solvent  action  of  car- 
bonic acid,  there  is  another  group  of  phenomena 
which  depend  upon  its  acid  character.  These 
must  now  be  explained.  They  are  the  neu- 
trality or  faint  alkalinity  of  the  ocean,  and  of 
protoplasm. 

According  to  the  modern  theory  of  solution, 
water  itself,  like  the  dissolved  electrolytes, 
is  dissociated  into  ions,  though  only  to  a  very 
slight  degree.^  The  reaction  is  expressed  as 
follows:  — 

HsO^H  +  OH 

and  the  deposit  of  the  material  so  removed  in  stalactites  and 
stalagmites,  likewise  the  rapid  effacement  of  marble  epi- 
taphs in  our  church  yards,  are  instances  of  this  solution.  .  .  . 
Among  the  sulphates,  gypsum  is  the  most  important  example 
of  solution.  It  is  dissolved  in  the  proportion  of  about  1 
part  in  400  parts  of  water.  Even  silica  is  abstracted  from 
rocks  by  natural  waters."  —  Geikie,  "Geology,"  pp.  451-452. 
^  For  a  discussion  of  this  subject  the  textbook  of  Mellor, 
*' Chemical  Statics  and  Dynamics,"  p.  205,  may  be  consulted. 


142    THE  FITNESS  OF  THE  ENVIRONMENT 

If  the  water  be  pure,  the  concentrations  of 
hydrogen  and  hydroxyl  ions  are  necessarily 
the  same,  for  water  is  electrically  neutral.  A 
variety  of  independent  methods  of  estimation 
have  shown  that  at  25°  (centigrade)  this 
concentration  amounts  almost  precisely  to 
O.OOOOOOIN,  in  the  ordinary  units.^  This 
corresponds  to  0.0000001  gram  of  ionized 
hydrogen  and  0.0000017  gram  of  ionized 
hydroxyl  in  1000  grams  of  water.  Further, 
the  theory  of  solution  explains  acidity  in 
water  by  the  occurrence  of  hydrogen  ions, 
formed  from  dissolved  electrolytes,  in  excess 
of  hydroxyl  ions ;  and  alkalinity  by  a  similar 
excess  of  hydroxyl  over  hydrogen  ions.  Neu- 
trality is  then  the  condition  when,  as  in  pure 
water,  the  two  concentrations  are  equal.  In 
short,  expressing  the  concentration  of  ionized 

^  Concentrations  are  expressed  in  terms  of  chemical 
equivalents,  gram-molecules,  or  moles.  A^  (normal)  is  the 
symbol  for  this  unit.  The  values  of  the  concentration  of 
ionized  hydrogen  at  neutrality  as  estimated  by  different 
investigators  are  as  follows  :  — 

6.      XlO-7  Kohlrausch  1884 

1.0  X10"7  Ostwald  1893 

1.1  XIO^  Arrhenius,  Shields         1893 

1.2  XIO'^  Wijs  1893 
0.9  XlO-7  Kanolt  1907 
1.02  X 10-7  Heydweiller  1909 
1.02X10-7  Lunden  1907 


CARBONIC  ACID  143 

+ 
hydrogen  by  (H)  and  of  ionized  hydroxyl  by 

(OH):- 

If  (H)  =  O.OOOOOOIN  =  (OH) 

the  solution  is  neutral; 

if  (H)  >  O.OOOOOOIN  >  (OH) 

the  solution  is  acid; 

if  (H)  <  O.OOOOOOIN  <  (OH) 

the  solution  is  alkaline. 

It  remains  to  point  out  that  implicit  in 
these  definitions  is  the  well-founded  hypothesis 
that  in  water  the  concentrations  of  hydrogen 
and  hydroxyl  ions  vary  inversely,  so  that 
with  constant  temperature  under  all  circum- 
stances their  product  is  constant :  ^  — 

(H)  X  (OH)  =  K 

Substituting  in  this  equation  the  value 
0.0000001  of  the  concentrations  at  neutral- 
ity, we  obtain  the  value 

K  =  0.00000000000001 
whence         (H)  =  0,00000000000001 

(OH) 

^  This  corresponds  with  the  requirements  of  the  Mass- 
Law. 


144     THE  FITNESS  OF  THE  ENVIRONMENT 

Whenever  a  weak  acid  is  present  in  aqueous 

solution    in    company    with    such    bases    ai 

sodium,  potassium,  calcium,  magnesium,  etc., 

which  are  invariable  constituents  of  the  ocean, 

blood,  protoplasm,  etc.,  provided  the  acid  he 

in  excess,  it  is  a  simple  matter  to  determine 

the  reaction,  which  can  best  be  measured  by 

+ 
the  values  of   (H)   and   (OH),  following   the 

considerations  above. 

Now  there  is  a  certain  characteristic  prop- 
erty of  an  acid,  its  ionization  constant,  k, 
which  measures  its  tendency  to  dissociate 
in  aqueous  solution,  thereby  to  produce  hydro- 
gen ions,  and  hence  to  increase  the  intensity 
of  acidity.  Strong  acids  have  ionization  con- 
stants which  are  of  the  order  of  magnitude  of 
1.0,  weak  acids  of  the  order  of  magnitude  of 
0.0001,  the  weakest  acids,  0.00000001,  or  less. 

Table  of  Ionization  Constants 

HCl,  HNO3,  etc 1. 

H3PO4       0.011 

H3ASO4 0.005 

HNO2 0.0005 

H2CO3        0.0000003 

NaH2P04        0.0000002 

H2S       0.000000091 

H3BO3        0.0000000007 

Na2HP04        0.00000000000036 

It  has  been  discovered  that  in  the  general 
case    above    discussed    the    concentration    of 


CARBONIC  ACID  145 

ionized  hydrogen  is  always  almost  exactly 
proportional  to  the  ratio  of  free  acid  to  salt, 
and  is  equal,  in  very  close  approximation, 
to  the  product  of  this  ratio  by  the  ionization 
constant  of  the  acid.  That  is  to  say,  repre- 
senting free  acid  by  HA  and  salt  by  BA, 

+ 

whence,  if  k=  (H) 

HA_. 
BA 

From  this  relationship,  therefore,  follows  the 
conclusion,  fully  established  by  experiment, 
that  whenever  in  such  a  solution  the  excess 
of  acid,  HA,  is  chemically  equivalent  to  the 
quantity  of  salt,  BA,  the  hydrogen  ion  concen- 
tration is  almost  exactly  equal  to  the  ioniza- 
tion constant  of  the  acid.  But  the  ionization 
constant  of  carbonic  acid  (first  hydrogen  atom) 
is  0.0000003.  Hence  in  a  solution  containing 
exactly  equivalent  quantities  of  free  carbonic 
acid  and,  for  example,  sodium  bicarbonate, 
the  hydrogen  ion  concentration  must  be 
0.0000003  N.     Further,  since 

HA_(H) 
BA       k 


be  the  case    (^;^-r  =  — )   the   value   must   be 


146    THE  FITNESS  OF  THE  ENVIRONMENT 

if  the  amount  of  acid  be  ten  times  the  amount 
of  salt  i^^-r  =  10  j,  the  hydrogen  ion  concentra- 
tion must  be  0.000003  N,  and  if  the  reverse 

HA 

BA 
0.00000003  N. 

The  range  of  variation  of  concentration  of 
hydrogen  ions  in  the  usual  solutions  of  the 
chemical  laboratory  considerably  surpasses 
the  limits  1.0  N  and  0.00000000000001  N.  In 
comparison  with  such  enormous  differences 
those  between  0.000003  N  and  0.00000003  N  are 
/  1     .  1 

100,000,000,000,000. 
Hence  ordinarily  it  is  quite  accurate  enough 
to  speak  of  any  solution  containing  both 
free  carbonic  acid  and  a  bicarbonate,  when 
the  disparity  between  the  concentrations  of 
the  two  substances  is  not  very  great,  as  of 
constant  neutral  reaction.  For,  obviously, 
the  neutral  point,  which  at  a  temperature  of 
25°  amounts  to  a  concentration  of  hydrogen 
and  hydroxyl  ions  0.0000001  N,  falls  well 
within  the  narrow  range  of  reaction  of  such 
solutions,  being  characterized  by  a  ratio  of 
carbonic  acid  to  bicarbonate  of  about  1:3. 

Thus  carbonic  acid,  like  the  almost  equally 
weak  acids  sulphuretted  hydrogen  and  phos- 


almost  negligible  I :  ^Y 

^  ^         UOO     100,000,000,000,0007 


CARBONIC  ACID  147 

phoric  acid  (after  its  first  hydrogen  has  been 
neutrahzed  by  base),  has  the  remarkable 
property  of  preserving  a  neutral  reaction 
whenever  it  exists  in  solution  with  its  salts, 
provided  there  be  an  excess  of  acid.  All  acids 
whose  strength  is  even  a  little  either  greater 
or  less  than  carbonic  acid  lack  the  property.^ 

This  characteristic  of  carbonic  acid  is  of 
the  utmost  significance,  first  by  regulating 
one  of  the  most  fundamental  of  physico- 
chemical  conditions,  and  secondly  by  pre- 
serving throughout  nature  the  characteristic 
chemical  inactivity  of  water,  which  disappears 
whenever  the  reaction  becomes  either  appre- 
ciably acid  or  appreciably  alkaline.  Almost 
the  only  case  of  important  geological  action 
due  to  acidity  or  alkalinity  of  water  is  the 
action  of  fresh  water,  containing  carbonic  acid 
itself,  to  weather  the  rocks.  This  process  is, 
however,  self -limited,  for  the  dissolved  material 
forms  bicarbonates,  and  thus  at  once  pro- 
vides permanently  inactive  balanced  solutions. 

It  is  impossible  to  understand  the  efficiency 
with  which  neutrality  is  preserved  by  carbonic 
acid,  without  the  actual  discussion  of  a  par- 
ticular case.     Let  us  therefore  consider  a  solu- 

^  Henderson,  "The  Relation  between  the  Strengths  of 
Acids  and  their  Capacity  to  Preserve  Neutrality,"  American 
Journal  of  Physiology,  XXI,  173,  1908. 


148     THE  FITNESS  OF  THE  ENVIRONMENT 

tion  of  1  kilogram  of  carbon  dioxide  in  100 
liters  of  water,  to  which  sodium  hydrate  is 
being  added.  At  the  beginning  of  the  experi- 
ment the  hydrogen  ion  concentration  will  be 
approximately  0.0001  N,  almost  exactly  one 
thousand  times  that  at  neutrality,  and  the 
hydroxyl  ion  concentration  0.0000000001  N, 
one  one-thousandth  that  at  neutrality.  If,  now, 
the  sodium  hydrate  be  added  to  the  solution 
in  successive  portions,  the  change  of  reaction 
will  be  as  indicated  in  the  following  table:  — 


Intensitt  compared  with 

Amount  of 

+ 
(H) 

(OH) 

A  Neutral  Solution  of 

NaOH 

Acidity 

Alkalinity 

Grams 

0 

0.0001  N 

0.0000000001  N 

1000 

0.001 

50 

0.0000052 

0.000000002 

52 

0.02 

100 

0.0000024 

0.000000004 

24 

0.04 

150 

0.0000015 

0.000000006 

15 

0.06 

200 

0.0000011 

0.000000009 

11 

0.09 

250 

0.0000008 

0.000000012 

8 

0.12 

300 

0.0000006 

0.000000017 

8 

0.17 

350 

0.0000005 

0.000000020 

5 

0.20 

400 

0.0000004 

0.000000025 

4 

0.25 

450 

0.0000003 

0.000000033 

3 

0.33 

500 

0.00000025 

0.00000004 

2.5 

0.4 

550 

0.00000020 

0.00000005 

2.0 

0.5 

600 

0.00000015 

0.00000007 

1.5 

0.7 

650 

0.00000012 

0.00000008 

1.2 

0.8 

700 

0.00000009 

0.00000011 

0.9 

1.1 

750 

0.00000006 

0.00000017 

0.6 

1.7 

800 

0.00000004 

0.00000025 

0.4 

2.5 

850 

0.00000002 

0.0000005 

0.2 

5.0 

CARBONIC   ACID  149 

From  the  table  it  appears  that  the  first 
50  grams  of  alkali  reduce  the  hydrogen  ion 
concentration  to  but  50  times  that  of  neutral 
solutions,  and  200  grams  of  alkali  have  made 
it  only  about  10  times  that  of  pure  water,  in 
spite  of  the  fact  that  there  are  more  than 
750  grams  of  free  carbonic  acid  still  present 
in  the  solution.  So  much  acidity  can  at  once 
be  obtained  by  dissolving  merely  0.004  gram 
of  hydrochloric  acid  in  100  liters  of  water. 
Thereafter  neither  acidity  nor  alkalinity  sur- 
passes this  intensity  until  450  grams  more  of 
sodium  hydrate  have  been  added  to  the  solu- 
tion. Yet  ill  pure  ivater  0.005  gram  of  sodium 
hydrate  would  make  the  reaction  more  alka- 
line than  that. 

Such  is  the  case  when  the  equilibrium  is 
homogeneous,  i.e.  in  an  isolated  solution. 
But  when,  in  similar  cases,  an  atmosphere 
containing  carbon  dioxide  is  present,  the  con- 
ditions are  still  more  striking.  Suppose,  for 
example,  a  solution  of  100  liters  containing  1 
kilogram  of  sodium  bicarbonate  in  equilib- 
rium with  an  atmosphere  containing  1  gram 
of  carbon  dioxide  per  liter.  Let  hydrochloric 
acid  be  added  in  successive  small  portions  to 
the  solution.  Further  let  the  solution  be 
constantly  stirred  and  shaken,  and  let  the 
experiment  be  conducted  slowly,  so  that  there 


150     THE  FITNESS  OF  THE  ENVIRONMENT 

shall  always  be  equilibrium  between  the  car- 
bonic acid  in  the  solution  and  in  the  atmos- 
phere. Further,  let  the  temperature  be  such 
that  the  absorption  coefficient  of  carbon 
dioxide  shall  be  1.000.  Then  the  successive 
states  of  the  solution  will  be  approximately 
as  recorded  in  the  following  table:  — 


HCl 

Added 

H2CO3: 
NaHCOs 

(H) 

(OH) 

Relative 
Acidity 

Relative 
Alka- 
linity 

Grams 
0 

2.27:11.9 

0.000000057  N 

0.000000176  N 

0.57 

1.76 

10 

2.27:11.5 

0.000000059 

0.000000170 

0.59 

1.70 

50 

2.27 :  10.0 

0.000000068 

0.000000147 

0.68 

1.47 

100 

2.27:  8.2 

0.000000083 

0.000000120 

0.83 

1.20 

150 

2.27:  6.3 

0.000000108 

0.000000093 

1.08 

0.93 

200 

2.27:  4.4 

0.000000154 

0.000000065 

1.54 

0.65 

250 

2.27:  2.6 

0.00000026 

0.000000039 

2.6 

0.39 

300 

2.27 :  0.68 

0.0000010 

0.000000010 

10 

0.10 

310 

2.27 :  0.31 

0.0000022 

0.0000000045 

22 

0.045 

318 

00 

0.00026 

0.00000000039 

260 

0.0039 

320 

0.00045 

0.00000000022 

450 

0.0022 

330 

0.0027 

0.000000000037 

2700 

0.00037 

From  the  beginning  of  the  experiment  until 
almost  250  grams  of  hydrochloric  acid  have 
been  added,  neither  alkalinity  nor  acidity  is 
double  in  intensity  the  values  which  obtain 
in  a  perfectly  neutral  solution.  This  amounts 
to  a  constancy  of  reaction  which,  until  a  few 
years  ago,  was  scarcely  known  to  the  chemist 
at    all.     Such    close    approach    to    neutrality 


CARBONIC   ACID  151 

can  be  attained  with  pure  water  only  after 
elaborate  and  very  difficult  purification,  yet 
in  the  presence  of  carbonic  acid  it  is  the  natural 
condition.  Of  course  the  case  above  dis- 
cussed is  an  extreme  one.  In  nature  the  con- 
centrations of  dissolved  substances  are  less, 
the  mixing  less  efficient,  and  the  variations  of 
reaction  a  little  greater.  There  is  also,  in 
nature,  likely  to  be  a  considerable  excess  of 
bicarbonate  over  free  carbonic  acid  present. 
The  cause  of  the  greater  constancy  of  re- 
action in  the  case  of  the  heterogeneous  equi- 
librium is  simple  enough.  At  the  beginning  of 
the  experiment  the  free  carbonic  acid  of  the 
solution  is  exactly  in  equilibrium  with  that  of 
the  atmosphere.  Accordingly,  when  hydro- 
chloric acid  is  poured  in  and  reacts  with  so- 
dium bicarbonate  to  form  sodium  chloride  and 
more  carbonic  acid, 

NaHCOs  +  HCl  =  NaCl  +  H2O  +  CO2 

every  bit  of  the  latter  escapes  to  the  atmos- 
phere, and  the  total  amount  of  acid  is  just 
what  it  was  before.  But  a  certain  amount  of 
carbonic  acid  has  been  replaced  by  the  equiv- 
alent amount  of  hydrochloric  acid.  This 
latter  substance,  however,  is  wholly  in  union 
with  sodium,  as  its  salt.  Thus  the  addition  of 
the    strong    acid    diminishes    the    amount    of 


152     THE  FITNESS  OF  THE  ENVIRONMENT 

alkaline  salt  (sodium  bicarbonate),  but  does 
not  increase  the  amount  of  free  acid.  Not 
until  the  bicarbonate  is  entirely  decomposed 
(318  grams  HCl)  does  the  hydrochloric  acid 
begin  to  exert  its  own  action  as  an  acid,  and 
then  2  grams  cause  about  as  much  rise  in 
acidity  as  318  grams  have  previously  caused, 
or  nineteen  times  the  rise  effected  by  the  first 
300  grams,  or  about  two  hundred  times  the 
rise  caused  by  one  hundred  times  the  quantity 
of  hydrochloric  acid  at  the  beginning  of  the 
experiment. 

These  statements  all  rest  upon  facts  which 
have  been  accurately  established  by  experi- 
ment and  are  brought  forward  in  company 
with  the  theoretical  treatment,  based  upon 
the  Mass  Law,  only  for  the  sake  of  complete- 
ness of  statement  and  because  brief  exposition 
is  otherwise  scarcely  possible.  The  extraor- 
dinary capacity  of  carbonic  acid  to  preserve 
neutrality  in  aqueous  solution,  which  is  ex- 
plained by  its  strength  and  solubility  in  water, 
is  a  well-established  experimental  fact,  and  no 
other  known  substance  shares  this  power. ^ 
Hydrogen  sulphide  might  perhaps  be  thought 
of  as  an  exception.     But  while  its  solubility 

^  Henderson,  "The  Theory  of  Neutrality  Regulation  in 
the  Animal  Organism,"  American  Journal  of  Physiology,  XXI, 
427,  1908. 


CARBONIC  ACID  153 

in  water  is  not  favorable  for  the  best  results, 
its  instability  is  a  fatal  obstacle. 

Such  are  the  physico-chemical  facts  re- 
garding neutrality  regulation  in  heterogeneous 
systems  by  means  of  carbonic  acid  and  bicar- 
bonates,  and,  though  the  exposition  is  difficult, 
it  has  seemed  necessary  to  make  them  clear. 
For  there  is,  I  believe,  except  in  celestial  me- 
chanics, no  other  case  of  such  accuracy  in  a 
natural  regulation  of  the  environment.  More- 
over, the  chemist  has  discovered  no  means  of 
rivaling  the  efficiency  and  delicacy  of  adjust- 
ment of  the  process.  Finally,  acidity  and 
alkalinity  surpass  all  other  conditions,  even 
temperature  and  concentration  of  reacting 
substances,  in  the  influence  which  they  exert 
upon  many  chemical  processes.^ 

Almost  wholly  through  this  mechanism  the 
oceans  are  always  nearly  neutral.  Chiefly 
with  its  aid  protoplasm  and  blood  possess  an 
unvarying  reaction.  Quite  recently  the  con- 
centration of  hydrogen  ions  in  the  ocean  has 
been    very    carefully    studied    by   Palitzsch,^ 

^  Of  all  catalytic  agents  these  ions  are  by  far  the  most 
important.  In  their  influence  upon  the  stability  of  colloidal 
systems  they  are  also  unapproached  by  other  substances. 

2  "  Etant  donne  que  I'eau  de  mer  a  un  contact  is  intime 
avec  les  organismes  de  la  mer  et  que  non  seulement  elle  les 
entoure  de  ses  flots,  mais  qu'elle  traverse  leurs  branchies  et 
impregne  en  partie  les  corp  des  invertebres,  il  semble  aesez 


154      THE  FITNESS  OF  THE  ENVIRONMENT 

who  finds  very  great  constancy,  the  extreme 
variations  (with  the  exception  of  the  Black 
Sea)  being  0.000000011  N  to  0.0000000045  N. 
Allowing  for  the  change  of  the  ionization 
constant  of  water  with  the  temperature,  and 
the  fact  that  in  such  systems  the  hydrogen 
ionization  is  nearly  independent  of  the  tem- 
perature, these  values  roughly  correspond  to 
hydroxyl  ion  concentrations  0.000002  N  and 
0.000005  N  respectively  at  the  lower  temper- 
atures and  slightly  higher  values  at  the  higher 
temperatures  of  sea  water.  This  is  a  sufficient 
excess  of  hydroxyl  ions  properly  to  be  termed 
faint  alkahnity,  though  it  amounts  to  but 
about  0.00005  gram  per  liter,  or  0.000005  per 
cent.  It  is  in  part  due  to  the  fact  that  the 
quantity  of  carbonic  acid  in  the  air  is  now 
very  small,  while  in  the  ocean  the  concentra- 
tion of  bicarbonates  is  great.  Indeed,  the 
ocean    has    unquestionably    grown    alkahne; 

justifie  de  la  placer  dans  la  meme  categorie  que  les  autres- 
liquides  physiologiques.  Des  determinations  exposes  dans 
ce  qui  precede  il  ressort  que,  de  meme  que  ces  liquides,  I'eau 
de  mer  est  douee  d'une  grande  capacite  de  regler  sa  concentra- 
tion en  ions  hydrogene,  bien  que  cette  capacite  soit  moins 
prononcee  que  celle  constatee  par  example  dans  le  sang." 
—  S.  Palitzsch,  "  Sur  le  mesurage  et  la  grandeur  de  la  concen- 
tration en  ions  hydrogene  de  I'eau  salee,"  Comptes-rendus 
des  travaux  du  Laboratoire  de  Carlsberg,  lOme  Volume, 
Ire  Livraison,  1911,  p.  93. 


CARBONIC  ACID  155 

for  its  origin  must  have  been  acid  from  the 
presence  of  carbonic  acid  unbalanced  by  base. 
The  present  ratio  between  bicarbonates  and 
carbonic  acid  in  sea  water  has  not  been  accu- 
rately estimated,  but  it  is  perhaps  50  : 1  or 
100:1.  The  conditions  are  complicated  by 
flora  and  fauna,  and  such  influences  have  not 
yet  been  determined. 

Turning  to  the  acid-base  equilibrium  of 
blood  and  protoplasm,  we  encounter  a  subject 
which  is  better  understood,  though  not  more 
significant  in  the  present  discussion.  The 
alkalinity  of  the  blood  is  one  of  the  familiar 
subjects  of  physiological  investigation,  and 
its  clinical  importance  has  long  been  clear. 
Not  until  the  introduction  of  the  ionization 
hypothesis,  however,  was  it  possible  to  explain 
the  conditions.  The  outcome  of  these  studies 
has  been  to  assign  to  the  equilibrium  between 
carbonic  acid  and  bicarbonates  a  first  place  in 
the  regulation  of  the  reaction  of  blood ;  ^  and 
since  such  substances  are  invariably  constitu- 
ents of  all  protoplasm,  to  make  evident  the 
universal  biological  importance  of  this  equi- 

^  Friedenthal,  "Archiv  fiir  Physiologic,  Verhandlungen 
der  Physiologischen  Gesellschaft  Berlin,"  May  8,  1903.  Hen- 
derson, American  Journal  of  Physiology,  XV,  257,  1906, 
"Ergebnisse  der  Physiologie,"  VIII,  254-325,  1909  (the  last 
a  review  of  the  equilibrium  between  acids  and  bases  in  the 
organism). 


156    THE  FITNESS  OF  THE  ENVIRONMENT 

librium.  The  process  is  complicated  by  the 
intervention  of  all  the  other  acids  and  bases 
of  the  body.  Of  these,  however,  only  phos- 
phates, and  in  lesser  degree  proteins,  are  im- 
portant. Thus  it  is  certain  that  in  the  one 
universal  chemical  equilibrium  of  protoplasm 
which  has  thus  far  been  defined  and  quantita- 
tively described  the  carbonates  take  a  prin- 
cipal part. 

It  is  not  possible  to  explain  the  significance 
of  carbonic  acid  in  this  physiological  process 
as  chiefly  an  adaptation ;  for  natural  selection 
can  have  nothing  to  do  with  the  occurrence  of 
carbonic  acid  in  the  living  organism,  or,  pre- 
sumably, with  the  nature  of  the  original 
living  things  upon  the  earth. ^  The  presence 
of  carbonic  acid  is  inevitable,  and  whatever 
the  first  forms  of  terrestrial  life  may  have 
been,  certain  it  is  that  carbonic  acid  was  one 
of  the  constituent  substances.  From  that  day 
to  this  it  has  steadily  fulfilled  the  function  of 
regulating  the  reaction  of  protoplasm,  and  of 
body  tissues  and  fluids. 

The  recent  studies  of  Hasselbach  and  Lunds- 
gaard^  indicate  that  the  hydrogen  ion  concen- 
tration of  normal  blood  at  body  temperature 

^  It  was  this  obvious  fact  which  originally  led  me  to  a  re- 
consideration of  fitness. 

2  '' Biochemische  Zeitschrift,  Vol.  38,  p.  77,  1912. 


CARBONIC  ACID  157 

is  about  0.000000044  N.  This  value  is  sub- 
ject to  constant  slight  variations,  diminish- 
ing as  the  blood  passes  through  the  lungs, 
increasing  during  the  greater  circulation;  but 
variations  of  this  kind  are  certainly  very 
slight  in  the  healthy  organism.  The  value 
corresponds  to  a  concentration  of  bicarbonates 
about  ten  times  as  great  as  that  of  free  car- 
bonic acid.  Together  the  acid  and  its  salts 
make  up  the  larger  part  of  all  the  carbonic 
acid,  and  a  very  considerable  fraction  of  all 
the  dissolved  molecules  of  the  blood.  In 
disease,  especially  diabetic  coma,  the  hydro- 
gen ion  concentration  may  rise  to  0.0000001  N, 
or  perhaps  higher ;  when  acid  is  injected  into 
the  blood  the  value  may  be  greater  still,  but 
death  speedily  ensues,  and  it  is  certainly  im- 
possible during  life  that  there  should  be  any 
considerable  permanent  variation. 

Increase  in  acidity  of  the  blood  can  occur 
only  in  association  with  marked  diminution 
in  the  concentration  of  bicarbonates,  which 
may  fall  to  less  than  one  third  of  their  normal 
amount,  greatly  impoverishing  the  blood  in 
respect  to  carbonic  acid,  and  interfering  with 
its  excretion.  This  is  due  to  the  fact  that 
the  amount  of  free  carbonic  acid  in  the  blood 
is  under  the  independent  control  of  the  respira- 
tory center,  and  when  acids  decompose  bicar- 


158    THE  FITNESS  OF  THE  ENVIRONMENT 

bonates  the  carbonic  acid  which  is  Hberated 
escapes  through  the  hmgs  into  the  air.  This 
action  is  analogous  to  the  simple  heterogeneous 
equilibrium  explained  above,  and  calls  for  no 
special  discussion. 

The  importance  of  this  physiological  equi- 
librium is  to  be  sought  in  part  in  one  of 
the  primary  characteristics  of  the  metabolic 
process,  —  the  chiefly  oxidative  formation  of 
acid.  In  the  main  the  foodstuffs  are  neutral 
substances,  but  their  principal  end  products, 
except  water,  are  almost  exclusively  acid 
compounds,  —  carbonic  acid,  phosphoric  acid, 
sulphuric  acid,  uric  acid.  Moreover,  there 
is  a  well  marked  tendency,  at  least  in  man  and 
the  vertebrates,  under  very  many  pathological 
conditions,  to  form  other  acids,  such  as  lactic 
acid,  ^-oxybutyric  acid,  acetoacetic  acid,  etc. 
This  tendency  toward  acidity  of  reaction  and 
the  accumulation  of  acid  in  the  body  is  one 
of  the  inevitable  characteristics  of  metabo- 
Hsm ;  the  constant  resistance  of  the  organism 
one  of  the  fundamental  regulatory  processes. 
Now  it  comes  about  through  the  carbonate 
equilibrium  that  the  stronger  acids,  as  soon  as 
they  are  formed,  and  wherever  they  are 
formed,  normally  find  an  ample  supply  of 
bicarbonates  at  their  disposal,  and  accordingly 
react  as  follows :  — 


CARBONIC  ACID  159 

HA  +  NaHCOs  =  NaA  +  H2CO3 

This  reaction  corresponds  exactly  to  the 
simple  case  first  discussed,  and  so  causes  an 
inconsiderable  change  in  the  concentration  of 
ionized  hydrogen.  The  free  carbonic  acid 
then  passes  out  through  the  lungs,  and  the 
salt  is  excreted  in  the  urine.  Other  processes 
are  involved,  including  a  device  for  final  re- 
tention of  a  part  of  the  alkali  which  has  neutral- 
ized acid,^  but  in  the  whole  complex  function 
nothing  is  more  important  than  the  simple 
reaction  written  above. 

The  hydrogen  ion  concentration  exerts  a 
marked  influence  upon  the  rate  of  progress 
of  chemical  reactions.  Thus,  for  example, 
the  so-called  inversion  of  cane  sugar  by  a  proc- 
ess of  hydrolytic  cleavage  into  glucose  and 
fructose, 

Ci2H220n  +  H2O  =  CeHi  A  +  CeHi^Oe, 

is  commonly  accomplished  by  warming  a  solu- 
tion of  sugar  to  which  a  little  acid  has  been 
added.  It  was  show^n  by  the  classical  investi- 
gation of  Wilhelmi  that  the  velocity  of  this 
process  depends  upon  the  strength  of  the 
acid,  or,  according  to  the  modern  view,  upon 

^  Henderson,  Journal  of  Biological  Chemistry,  IX,  403, 
1911. 


160    THE  FITNESS  OF  THE  ENVIRONMENT 

the  concentration  of  hydrogen  ions.  Indeed, 
these  ions  are  the  effective  agents  in  the 
process. 

Reactions  of  this  type,  in  which  carbohy- 
drates, fats,  proteins,  and  other  substances 
take  part,  make  up  a  very  large,  if  not  the 
largest  fraction  of  all  the  processes  of  metabo- 
lism, and  there  can  be  no  doubt  that  for  their 
regulation  very  accurate  adjustment  of  acidity 
and  alkalinity  is  essential.  In  the  body,  to 
be  sure,  such  reactions  are  under  the  control  of 
enzymes,  but  the  concentration  of  hydrogen 
and  hydroxyl  ions  is  not  less,  rather  more 
important  for  that  reason.  Beside  retaining 
their  direct  influence  upon  the  reaction,  the 
ions  also  exert  an  influence  upon  the  enzymes 
themselves.  Moreover,  not  only  enzymes,  but 
almost  all  colloidal  bodies,  especially  such 
unstable  structures  as  the  colloids  of  proto- 
plasm, are  profoundly  affected  by  changes  of 
reaction,  and  for  the  preservation  of  their 
stability  they  also  are  absolutely  dependent 
upon  constancy  of  acidity  and  alkalinity. 

Finally,  it  is  to  be  noted  that  glucose,  which 
is  the  principal  source  of  energy  in  physiolog- 
ical processes,  is  very  unstable  in  even  faintly 
alkaline  solutions,  and  that  its  stability  varies 
in  most  marked  degree  with  the  slightest 
change    in    the    concentration    of    hydroxyl 


CARBONIC  ACID  161 

lons.^  Further,  there  is  also  reason  to  be- 
lieve that  the  concentration  of  hydrogen  and 
hydrox^^l  ions  may  sometimes  be  concerned 
in  adjustments  of  great  magnitude,  which 
involve  the  distribution  of  water  between  the 
tissues  and  the  body  fluids,  or  at  least  be- 
tween red  blood  corpuscles  and  the  plasma.^ 
Recently,  for  example,  a  theory  has  been  sug- 
gested which  seeks  to  account  for  certain 
forms  of  oedema  as  the  result  of  local  or  general 
increase  in  the  acidity  of  the  organism.^ 
In  any  case,  whatever  the  fate  of  these  latter 

^  Henderson,  Journal  of  Biological  Chemistry,  X,  3,  1911. 

2  The  changing  distribution  of  material  between  red 
blood  corpuscles  and  plasma  as  the  tension  of  carbonic  acid 
changes  has,  since  its  discovery  by  Zuntz,  been  investigated 
by  a  series  of  physiologists.  (See  Spiro  and  Henderson, 
.Biochemische  Zeitschrift,  15,  114,  1908.)  In  each  complete 
cycle  of  the  circulation  there  occurs  a  complete  cycle  of  changes 
between  the  constituents  of  the  corpuscles  and  of  the  plasma. 
As  the  blood  passes  tlu-ough  the  tissues  and  receives  carbonic 
acid  the  volume  of  the  red  corpuscles  increases  from  the 
entrance  of  water  coming  from  the  plasma ;  chlorine  simul- 
taneously passes  in  the  same  direction ;  and  various  other 
changes  occur.  In  the  lungs,  with  the  escape  of  carbonic 
acid,  the  process  is  reversed.  There  seems  to  be  no  doubt 
that  this  process  is  largely  dependent  upon  changes  in  re- 
action accompanying  changes  in  the  concentration  of  carbonic 
acid. 

3  M.  H.  Fischer,  "(Edema,"  New  York,  1910.  It  is  impos- 
sible to  judge  of  the  correctness  of  many  of  the  views  set 
forth  in  this  work.  At  present  they  appear  to  be  in  part  ill- 
founded. 


162    THE   FITNESS  OF  THE  ENVIRONMENT 

views  may  be,  the  common  physiological 
processes,  and  the  structural  conditions  which 
depend  for  their  integrity  upon  constancy  of 
the  concentration  of  hydrogen  and  hydroxyl 
ions  are  certainly  manifold. 

The  principal  conditions  and  processes, 
both  inorganic  and  organic,  which  rest  upon 
the  acid  nature  of  carbonic  acid  and  its  char- 
acteristic distribution  between  the  atmos- 
phere and  aqueous  solutions  have  now  been 
indicated.  In  their  origin  at  least  they  are 
nowise  due  to  the  agency  of  organic  evolution. 
Yet  directly,  because  of  the  nature  of  carbon 
dioxide  as  a  gas,  because  of  its  solubility  in 
water,  and  on  account  of  the  precise  degree 
of  its  weakness  as  an  acid,  they  possess  the 
highest  possible  efficiency.  This  conclusion 
might  be  established  with  rigorous  accuracy 
by  means  of  a  mathematical  analysis,  but  the 
above  discussion  is  sufficient  for  the  present 
purpose.^ 

In  this  manner  carbonic  acid  shows  itself 
in  its  physico-chemical  traits  variously  fitted 
for  the  organic  mechanism.  Less  various,  to 
be  sure,  and  less  obvious  than  those  of  water> 
such  fitnesses  as  it  does  possess  are  quite  as 

1  Henderson,  American  Journal  of  Physiology,  XXI,  173, 
1908. 


CARBONIC   ACID  163 

genuine.  But  they  are  dependent  upon  water ; 
secondary  in  their  nature ;  resting  upon  sohi- 
bihty  and  ionization;  upon  interactions  be- 
tween the  two  substances.  So  they  lead  us 
to  a  consideration  of  the  most  intricate  of 
all  mutual  relations,  to  a  purely  chemical 
study  of  the  compounds  of  carbon,  hydrogen, 
and  oxygen,  into  which  water  and  carbonic 
acid  can  be  transformed. 


CHAPTER  V 

THE   OCEAN 

AT  every  stage  of  our  inquiry  we  have  seen 
that  the  unique  properties  of  water  and 
carbonic  acid  contribute  vitally  important 
characteristics  to  the  ocean.  Such  conclusions 
accord  with  the  ordinary  experiences  of  life, 
and  they  gain  in  significance  from  the  un- 
doubted fact  that  organic  beings  first  existed, 
and  for  a  very  long  time  existed  only  in  the 
waters.  On  this  account  it  will  be  well  to  pause 
before  attacking  the  problems  of  organic 
chemistry,  and,  in  somewhat  greater  detail, 
to  examine  the  ocean  in  its  relation  to  the 
inhabitants  of  the  globe.  Thus  we  shall  be 
able  more  clearly  to  perceive  the  manner  in 
which,  in  one  most  important  instance,  the 
properties  of  water  and  carbonic  acid  operate 
to  fit  the  world  for  life. 


THE  REGULATION  OF  PHYSICO-CHEMICAL 
CONDITIONS 

The  most  striking  of  all  the  ocean's  qualities 
is  its  constancy.     No  doubt  since  its  origin 

164 


THE  OCEAN 


165 


it  has  grown  colder  and  more  saline,  and  has 
changed  its  reaction  from  faintly  acid  to 
faintly  alkaline.  But  a  million  years  are  little 
in  such  great  slow  processes,  and  no  living 
thing  has  ever  experienced  appreciable  change 
in  any  one  of  them. 

Modern  research  in  oceanography  has  de- 
tected surprisingly  little  variation  in  the  tem- 
perature of  the  ocean. ^  The  temperature  of 
surface  water  depends  upon  the  climatic 
character  of  the  locality,  but  it  is  subject  to 
far  less  variation  than  the  temperature  of  the 
atmosphere  above  it,  and  is  higher  than  the 
latter.  The  accompanying  tables  ^  indicate 
the  nature  of  some  of  the  variations  in  the 
temperature  of  sea  water. 


Annual  Ranges  of  Temperatures  of  Ocean  Water 

AND  OF  THE  AlR  OvER  LaND 


Latitude 

Ocean 

0° 
2.3 

10° 
2.4 
3.3 

20° 
3.6 

7.2 

30° 
5.9 
10.2 

40° 
7.5 
14.0 

50° 
5.6 

Land 

25  A 

^  Nearly  all  the  facts  contained  in  the  present  chapter  have 
been  drawn  from  the  following  works  :  S.  Giinther,  "Hand- 
buch  der  Geophysik  "  ;  Arrheniiis,  "Kosmische  Physik  "  ;  and 
Hann's  "Climatology,"  translated  by  Ward. 

2  See  Hann's  "Climatology,"  translated  by  Ward,  p. 
135. 


166    THE  FITNESS  OF  THE  ENVIRONMENT 


Water  and  Air  Temperatures  at  Lesina 


Winter 

Spring 

Summer 

Autumn 

Yeah 

R.VNGE 

Air 

9.2° 

14.8° 

24.4° 

17.9° 

16.6° 

15.2° 

Surface  water  .     . 

13.5 

15.0 

22.0 

19.5 

17.5 

8.5 

Water  at  10  meters 

13.9 

14.7 

20.3 

18.4 

16.8 

6.4 

According  to  Schott  the  variation  of  surface 
temperature  of  the  open  ocean  over  the  whole 
globe  is  never  less  than  1°  nor  more  than  15°. 
Such  variations  are  slight  on  the  equator, 
larger  in  the  region  of  the  trade  winds,  less 
again  in  the  northern  and  southern  seas.^ 
The  surface  temperature  extends  only  a  short 
distance  into  the  water,  thus  constituting  a 
warm  surface  layer.  It  has  indeed  been 
known  since  the  time  of  Aristotle  that  the 
depths  of  the  sea  are  cold.  In  the  open 
ocean  the  temperature  increases  steadily  as 
the  depth  increases,  but  more  rapidly  near 
the  surface,  more  slowly  at  greater  depths. 
The  bottom  water  at  great  depth  varies  from 
a  temperature  of  2°  in  the  tropics  to  about 
—  2°  in  the  polar  waters.  Such  low  temperature 
of  the  depths  of  the  tropical  oceans  is  almost 
certainly  due  to  the  inflow  of  cold  water  from 
high  latitudes. 


^  Arrhenius,  I.e. 


THE  OCEAN  167 

In  the  Atlantic  the  temperature  varies  ap- 
proximately as  follows  with  increasing  depth: — ■ 


:  IN  Meters 

Temperature  Centigeadb 

0 

19° 

500 

16 

1000 

9 

1500 

4 

2000 

3 

2500 

2.5 

3000 

2 

In  the  Mediterranean,  where  no  cold  cur- 
rent flows  in  at  the  bottom  of  the  ocean,  the 
temperature  sinks  rapidly  to  11°  at  a  short 
distance  below  the  surface,  and  thereafter  re- 
mains constant.  This  is  due  to  the  fact  that 
in  winter  the  surface  water  is  cooled  to  that 
temperature  and  sinks,  remaining  then  pro- 
tected from  the  summer  heat  by  the  warmer 
layer  of  less  density  above. 

The  slight  range  of  ocean  temperatures, 
whether  with  changing  seasons,  with  chang- 
ing depth,  or  with  changing  latitude,  depends 
primarily  upon  the  latent  heat  of  water, 
especially  its  heat  of  vaporization,  and  upon 
the  very  high  freezing  point,  as  already  ex- 
plained in  the  discussion  of  these  physical 
properties. 

Far  more  constant  than  the  temperature  is 
the  alkalinity  of  sea  water.  It  has  been  stated 
above  that  the  extreme  variation  in  concentra- 


168     THE  FITNESS  OF  THE  ENVIRONMENT 

tion  of  ionized  hydrogen  is  from  0.000000011  N 
to  0.0000000045  N.  In  his  studies  during  a 
voyage  of  five  months  in  the  summer  season 
of  1910  of  the  Danish  steamship  Thor,  Palitzsch 
made  the  following  observations:  ^  surface 
water  from  the  Skager-Rack,  from  the  south- 
ern portions  of  the  North  Sea,  and  from  the 
west  of  the  Baltic  ranged  from  about 
0.000000010  N  to  about  0.000000009  N  ;  in  the 
North  Sea  the  surface  water  varied  from 
0.0000000083  N  to  0.0000000074  N ;  at  the  lati- 
tude of  Murray  Firth,  twenty  miles  from  the 
coast,  the  values  were  between  0.0000000071  N 
and  0.0000000066  N.  In  the  Atlantic  the 
surface  water  corresponded  in  the  most  north- 
ern portions  to  that  of  the  North  Sea,  while  in 
the  Bay  of  Biscay  and  along  the  coast  of 
Portugal  the  values  were  0.0000000056  N, 
corresponding  to  slightly  increased  alkalinity, 
especially  if  account  be  taken  of  the  rising 
temperature.  In  general  the  waters  of  the 
Mediterranean  corresponded  to  those  of  the 
coast  of  Portugal.  But  from  the  Sea  of  Mar- 
mora, the  Bosphorus,  and  the  Black  Sea 
samples  were  obtained  which  gave  the  value 
0.0000000045  N. 

In    general,  as    the    depth    increased,  the 

1  Palitzsch,   "  Comptes-rendiis  des  travaux  du  Laborataire 
de  Carbberg,"  lOme  Volume,  p.  85,  1911. 


THE  OCEAN 


hydrogen    ion    concentration    increased, 
the  alkalinity  accordingly  diminished. 


169 


and 


Depth  in 
Meters 

+ 
(H)  X  100,000,000 

Mediterranean 

Atlantic 

North  Sea 

Black  Sea 

0 

0.59 

0.60 

0.74 

0.46 

10 

0.56 

25 

0.65 

50 

0.59 

0.66 

0.71 

75 

0.93 

85 

1.03 

100 

0.62 

0.74 

0.81 

1.38 

200 

0.65 

0.83 

2.1 

300 

2.8 

400 

0.65 

0.91 

0.93 

3.0 

600 

0.98 

700 

1.05 

800 

0.68 

0.98 

1000 

0.72 

0.98 

1200 

0.72 

1.05 

1500 

0.76 

1.13 

2000 

0.81 

1.13 

2500 

0.85 

3200 

0.85 

The  only  variation  from  the  truly  remark- 
able constancy  of  reaction  of  the  ocean,  so 
far  as  we  know,  is  in  the  case  of  the  Black  Sea. 
But  this  sea,  at  depths  below  180  meters,  con- 
tains sulphurous  acid,  which  undoubtedly 
accounts  for  the  slight  diminution  of  alkalin- 
ity recorded  in  the  table.      This  last  obser- 


170     THE  FITNESS  OF  THE  ENVIRONMENT 

vation  also  provides  a  striking  example  of 
the  efficiency  with  which  the  reaction  of  sea 
water  is  maintained.  In  spite  of  the  unusual 
circumstances  here  the  variation  is  inconsider- 
able. The  only  known  important  factor  which 
operates  to  establish  and  to  preserve  the  re- 
action of  sea  water  is  the  carbonate  equilib- 
rium. 

There  is  one  consideration  which  must  be 
especially  noted  before  passing  on.  The  most 
obvious  effect  of  slight  changes  of  temperature, 
and  of  slight  changes  of  alkalinity  as  well, 
is  upon  the  velocity  of  chemical  reactions. 
In  this  respect  the  effect  of  hydroxyl  ions  is 
likely  to  be  in  proportion  to  their  concentra- 
tion,^ and  the  effect  of  temperature  is  usually 
such  that  a  change  of  about  ten  degrees  doubles 
the  velocity  of  the  reaction.^  Hence  ordinary 
chemical  reactions  will  progress  about  eight 
times  as  fast  in  the  hottest  as  in  the  coldest 
ocean  waters,  and  about  seven  times  as  fast 
in  the  most  alkaline  as  in  the  least  alkaline 
parts  of  the  ocean.  But  in  the  case  of  any 
organism  inhabiting  a  particular  locality  such 
changes  in  reaction  velocity  will  be  scarcely 

^  The  chief  actions  of  hydroxyl  ions  are  catalytic,  and,  as 
in  the  case  of  the  catalysis  of  esterification,  the  effect  is  pro- 
portional to  the  concentration  of  the  hydroxyl  ions. 

2  This  observation  is  due  to  van't  Hoff. 


THE  OCEAN 


171 


appreciable.     Accordingly,  the    regulation    is 
physiologically  adequate. 

The  concentration  of  sea  water  is  another 
nearly  constant  characteristic,  though  gener- 
ally speaking  the  salinity  is  somewhat  greater 
on  the  high  seas  than  near  the  coasts,  where 
fresh  water  is  constantly  diluting  the  salt 
water,  and  there  are  some  other  causes  which 
produce  slight  variations.  The  average  salt 
content  is  about  3.45  per  cent.  The  quan- 
tities of  the  more  important  constituents, 
calculated  from  Dittmar's  data,^  are  as  fol- 
lows :  — 


Per  Cent 


Relative  Amount 


Sodium,  Na    . 
Magnesium,  Mg 
Calcium,  Ca  .     . 
Potassium,  K 
Chlorine,  CI    .     , 
Sulphate,  SO4 
Carbonate,  CO3 
Bromine,  Br  .     . 


1.049 
0.130 
0.041 
0.038 
1.896 
0.263 
0.007 
0.006 


30.59 
3.79 
1.20 
1.11 

55.27 
7.66 
0.21 
0.19 


Most  of  the  other  numerous  constituents  are 
present  in  very  small  quantities.  For  in- 
stance, in  each  metric  ton  of  sea  water  there 


^  Dittmar,  Report  of  Voyage  of  the  Challenger,  1884,  p. 
203.  The  original  data  were  calculated  upon  the  erroneous 
assumption  that  the  various  salts  exist  in  solution  independ- 


172    THE   FITNESS  OF  THE  ENVIRONMENT 

are  dissolved  about  0.019  gram  of  silver  and 
about  0.006  gram  of  gold,  amounts  which 
correspond  to  0.0000019  per  cent  and 
0.0000006    per    cent,    respectively. 

It  has  been  calculated  that  166,000,000 
years  have  been  required  for  the  streams  to 
carry  into  the  sea  the  sodium  chloride  which 
is  now  present.  The  calcium  carbonate  of 
the  rivers  would  however  suffice  to  supply 
the  present  amount  of  that  substance  in  500,- 
000  years.  Accordingly,  the  present  store  of 
the  latter  substance  represents  but  a  very 
small  fraction  of  what  has  passed  through  the 
ocean,  and  as  a  result  of  the  intervention  of 
life  has  finally  been  deposited  as  sedimentary 
limestone.  Since  the  formation  of  the  ocean, 
if  present  conditions  correspond  with  the  past, 
water  must  have  carried  to  the  dwellers  of 

ently  of  one  another.  Thus  the  composition  of  sea  water  is 
stated  as  follows  :  — 


Sodium  chloride,  NaCl  .  . 
Magnesium  chloride,  MgCl2  . 
Magnesium  sulphate,  MgS04 
Calcium  sulphate,  CaS04 
Potassium  sulphate,  K2SO4  . 
Calcium  carbonate,  CaCOa  . 
Magnesium  bromide,  MgBr2 


Relative 
Amount 


77.758 
10.878 
4.737 
3.600 
2.465 
0.345 
0.217 


THE  OCEAN  173 

the  sea  not  less  than  300,000,000,000,000,000 
tons  of  calcium  carbonate,  which  they  have 
temporarily  utilized  as  structural  material. 
Whether  this  estimate  be  correct  or  not,  the 
process  is  certainly  the  cause  of  the  most 
considerable  change  wrought  by  life  upon  the 
face  of  the  earth. 

The  relative  quantities  of  the  several  saline 
constituents  of  the  ocean  are  hardly  at  all 
subject  to  variation.  Chlorine,  for  example, 
makes  up  never  less  than  55.21  per  cent  and 
never  more  than  55.34  per  cent  of  all  the  dis- 
solved inorganic  substances,  so  that  the  total 
salinity  may  be  readily  estimated  with  consid- 
erable accuracy  by  titration  of  the  chlorides. 
Such  constancy  is  due  to  the  elaborate  mixing 
of  the  waters  resulting  from  ocean  currents. 
There  can  be  no  doubt,  however,  that  the 
relative  amounts  of  the  different  acids  and 
bases  have  slowly  but  steadily  changed  during 
the  progress  of  geological  evolution.  Many 
substances,  like  calcium  carbonate,  have  been 
steadily  removed,  a  few,  like  sodium  chloride, 
have  steadily  accumulated  without  loss. 

The  total  salinity  of  the  ocean,  as  stated 
above,  is  subject  to  slight  variation.  Along 
the  North  American  coast,  in  the  polar  cur- 
rent, upon  the  coast  of  Norway,  and  toward 
the  south  of  South  America,  the  concentration 


174    THE   FITNESS  OF  THE  ENVIRONMENT 

of  the  Atlantic  is  3.2  per  cent  to  3.3  per  cent. 
Areas  where  the  concentration  ranges  from 
3.3  per  cent  to  3.4  per  cent  are  still  more 
extensive.  The  greater  part  of  the  North 
Atlantic  ranges  in  concentration  from  3.5 
per  cent  to  3.6  per  cent.  In  general  there  is  a 
region  of  maximum  concentration  between  the 
Equator  and  the  Pole. 

The  Mediterranean,  the  Red  Sea,  and  other 
similar  bodies  of  water  possess  a  somewhat 
higher  salt  concentration,  dependent  upon 
excessive  evaporation  and  the  absence  of 
great  currents ;  but  only  in  exceptional  cases 
and  small  isolated  bodies  of  water  does  the 
concentration  rise  above  4.1  per  cent. 

The  salinity  of  ocean  water  varies  also  with 
the  depth.  In  seas  where  there  is  a  great 
influx  of  fresh  water  the  surface  is  less  con- 
centrated than  the  depths;  in  seas  where 
there  is  much  evaporation  the  surface  is  more 
concentrated  than  the  depths.  In  the  latter 
case  the  higher  temperature  of  the  surface 
causes  expansion  of  the  more  concentrated 
water,  and  enables  it  to  remain  above.  When 
these  two  influences  of  dilution  and  evapora- 
tion are  combined,  they  may  bring  about  a 
yearly  variation  of  salinity.  Such  variations 
of  the  environment  are  important  to  animal 
life,  slight  though  they  may  be.     Thus  the 


THE  OCEAN  175 

herring  in  their  migrations  keep  to  a  water 
whose  concentration  ranges  from  3.2  per 
cent  to  3.3  per  cent. 

From  the  constancy  of  the  relative  pro- 
portion of  the  salts  in  sea  water  it  follows  that 
every  such  constituent  is  subject  to  no  greater 
variations  than  the  sum  of  all.  Interesting 
recent  experiments  have  shown  this  fact  to 
be  of  vital  consequence  to  living  organisms. 
Thus  a  host  of  experiments  of  Loeb  and  his 
pupils,  and  of  others,  have  demonstrated  re- 
markable toxicity  in  the  action  of  pure  salts, 
physiologically  antagonistic  actions  of  vari- 
ous pairs  of  salts,  and  peculiar  advantages  of 
media  containing  a  variety  of  salts  in  definite 
relative  amounts.^  Of  all  such  balanced  solu- 
tions sea  water  is  by  far  the  best,  a  condition 
which  is  almost  certainly  due  to  the  processes 
of  organic  evolution.  Herbst  ^  has  shown 
that  the  development  of  the  fertilized  eggs 
of  sea  urchins  can  only  take  place  in  the 
presence  of  the  chlorides,  sulphates,  and  car- 
bonates of  sodium,  potassium,  calcium,  and 
magnesium,  and  in  a  faintly  alkaline  reaction. 
Every   one   of  these   substances   is   essential, 

^  See  the  article  by  Loeb  in  Oppenheimer's  "Handbuch 
der  Biochemie." 

^  Herbst,  Archiv.fiir  Entwickelungsmechanik,  5,  650,  1897; 
7,  486,  1898;    11,  617,  1901;    17,  306,  1904. 


176     THE   FITNESS  OF  THE  ENVIRONMENT 

except  that  in  a  measure  potassium  may  be 
replaced  by  rubidium  and  caesium,  and  chlo- 
rine by  bromine.  Moreover  the  relative  con- 
centrations are  of  the  highest  importance. 
Thus  it  has  become  clear  that  the  remark- 
able relative  and  absolute  constancy  of  the 
chemical  composition  of  sea  water  is  biolog- 
ically far  more  important  than  formerly 
could  be  surmised.  This  characteristic  of 
the  ocean  undoubtedly  fits  it  for  living 
things  as  they  exist. 

It  is  further  to  be  noted  that  the  salinity  of 
sea  water  is  proportional  to  its  osmotic  pres- 
sure. This  important  property  also  is  there- 
fore nearly  constant. 

When  a  solution  is  inclosed  in  a  membrane, 
a  bladder,  for  example,  and  the  latter  is  im- 
mersed in  water,  both  water  and  dissolved 
substance  pass  through  the  wall  of  the  mem- 
brane. Ordinarily,  however,  the  water  will 
move  much  more  rapidly  than  the  dissolved 
substance,  hence  the  volume  of  the  solution 
will  increase,  and  hydrostatic  pressure  will 
be  established.  If  a  well-supported  mem- 
brane of  cupric  ferrocyanide  be  substituted 
for  the  bladder,  the  process  will  be  modified, 
in  that  water  alone,  not  the  dissolved  sub- 
stance, can  pass  through  the  membrane, 
which  is   accordingly  termed  semipermeable. 


THE  OCEAN  177 

Under  these  circumstances  the  pressure,  called 
osmotic  pressure  by  van't  Hoff,  may  be  very 
great. 

According  to  the  theories  of  van't  Hoff 
and  Arrhenius  this  pressure  is,  in  the  case  of 
dilute  solutions,  proportional  to  the  total 
number  of  particles  (molecules  plus  ions) 
which  are  present  in  solution.  In  its  magni- 
tude and  the  laws  governing  its  variation  such 
pressure  corresponds  exactly  to  gaseous  pres- 
sure. In  fact  the  theory  of  solution  consists 
primarily  in  the  extension  of  the  laws  of  Boyle 
and  Gay-Lussac,  of  the  hypothesis  of  Avo- 
gadro,  and  of  the  manifold  theoretical  develop- 
ments which  have  been  based  upon  them,  to 
solutions.  The  great  force  of  osmotic  pres- 
sure always  comes  into  action  when  solutions 
are  in  contact  with  permeable  or  semiper- 
meable membranes.  It  must  therefore  al- 
ways be  reckoned  with  in  physiology.  The 
biological  importance  of  the  constancy  of  the 
osmotic  pressure  of  sea  water  is  strikingly 
exemplified  by  the  precision  with  which  every 
higher  vertebrate  preserves  constant  the  os- 
motic pressure  of  its  own  body  fluids,  all  at 
about  seven  or  eight  atmospheres. 

It  may  readily  be  shown  that  the  osmotic 
pressure  of  a  solution  is  proportional  to  the 
depression  of  its  freezing  point,  and  accord- 


178     THE  FITNESS  OF  THE  ENVIRONMENT 

ingly  osmotic  pressure  is  commonly  estimated 
with  the  help  of  this  relationship.  In  the 
following  table  the  facts  regarding  blood  sera 
of  certain  animals  are  collected.^ 

Depression  of  the  Freezing  Point  of  Blood  Serum 

Degree 

Man 0.526 

Cow 0.585 

Horse 0.564 

Pig 0.615 

Rabbit 0.592 

Dog 0.571 

Cat 0.638 

Sheep 0.619 

In  man  the  freezing  point  depression  of  the 
blood  is,  under  ordinary  circumstances,  practi- 
cally constant,  and  there  can  be  no  doubt  that 
such  is  the  case  for  all  highest  organisms. 
Accordingly  the  differences  in  the  above  table 
may  be  taken  to  indicate  slight  constant  dif- 
ferences between  the  different  species. 

The  marine  animals,  except  a  few  of  the 
vertebrates,  are  adjusted  in  their  osmotic 
pressures  to  the  water  which  surrounds  them. 
As  in  the  following  table  so  in  another  lo- 
cality where  the  freezing  point  of  the  water 
was  —1.9°  the  body  fluids  of  the  animal 
were  again  found  to  agree  with  it.  It  is 
therefore    evident  that  constancy  of  osmotic 

1  Hober,  "Physikalische  Chemie  der  Zelle  und  der  Gewebe.'* 


THE  OCEAN  179 

pressure  is  for  marine    animals    a   matter  of 
real  moment. 

Depressions  of  the  Freezing  Point 

Degrees 

Coelentrate,  Alcyonium  palmatum 2.196 

Echinoderm,  Asteropecten  aurantiacus 2.312 

Echinoderm,  Holothuria  tubulosa 2.315 

Worm,  Sipunculus  nudus         2.31 

Crustacean,  Maja  squinada 2.36 

Crustacean,  Homarus  vulgaris 2.29 

Cephalopod,  Octopus  macropus 2.24 

Selachian,  Torpedo  marmorata 2.26 

Selachian,  Mustelus  vulgaris 2.36 

Selachian,  Trygon  violacea       2.44 

Teleost,  Charax  puntazzo 1.04 

Teleost,  Cerna  gigas 1.035 

Teleost,  Crenilabrus  pavo 0.74-0.76 

Teleost,  Box  salpa 0.82-0.88 

Reptile,  Thalassochelys  caretta 0.61 

Sea  Water 2.3 

The  great  importance  of  osmotic  pressure 
is  also  attested  by  many  of  the  facts  of  phys- 
iology. The  study  of  this  subject  has  in- 
deed from  its  origin  always  been  closely 
associated  with  the  biological  sciences,  and  it 
was  in  great  part  biological  experiments  and 
wholly  experiments  of  biologists  which  were 
employed  by  van't  Hoff  in  his  development, 
on  the  basis  of  osmotic  phenomena,  of  the 
theory  and  laws  of  dilute  solutions. 

Absorption,  secretion,  excretion,  and  the 
movement  of  substances  across  membranes, 


180     THE   FITNESS  OF  THE  ENVIRONMENT 

—  to  say  nothing  of  the  estabhshment  of 
liquid  currents  within  the  body,  —  are  all 
related  to  osmotic  pressure.  The  forces  in- 
volved in  such  processes  are  large,  and  osmotic 
phenomena  assume  a  special  importance 
wherever  colloidal  systems  occur.  It  appears 
to  be  certain  that  osmotic  pressure  is  now  se- 
curely established  as  one  of  the  fundamental 
factors  in  the  physico-chemical  organization  of 
the  living  mechanism,  and  one  of  the  constant 
conditions,  like  concentration  of  the  several 
constituents,  alkalinity,  temperature,  etc., 
whose  preservation  is  of  vital  importance. 


II 

THE  CIRCULATION  OF   WATER 

There  are  a  number  of  causes  which  bring 
about  ocean  currents.  In  the  tropics  high 
temperature  causes  a  far  greater  evaporation 
of  water  than  can  be  offset  by  rainfall  and  the 
flow  of  rivers;  near  the  poles  this  relation  is 
reversed.  Hence  water  must  steadily  flow 
from  high  to  low  latitudes,  there  to  evaporate 
and  complete  the  cycle  in  the  atmosphere  and 
on  the  land.  In  polar  regions  the  cold  water 
sinks  and  penetrates  along  the  bottom  of  the 
sea  in  great  deep  currents  to  the  tropics. 


THE  OCEAN  181 

The  surface  currents  of  the  ocean  have  a 
different  origin,  for  they  depend  upon  winds, 
especially  trade  winds,  etc.  Such  continuous 
action  of  moving  air  upon  w^ater  has  been 
theoretically  explained  by  Helmholtz  and 
Zopperitz.  Needless  to  say,  in  addition  to 
these  principal  causes  there  are  a  great  variety 
of  lesser  factors  which  assist  in  the  formation 
and  preservation  of  ocean  currents. 

It  is  impossible  here  to  undertake  an  analy- 
sis of  the  phenomenon,  but  certain  it  is  that 
into  the  processes  that  constantly  stir  the 
ocean,  beside  the  rotation  of  the  earth,  the 
eccentricity  of  its  orbit,  and  the  inclination  of 
its  axis,  the  thermal  properties  of  w^ater  enter 
as   fundamentally   important   factors. 

The  magnitude  and  the  extent  of  the 
movements  which  result  from  such  influences 
are  very  considerable.  The  principal  surface 
currents  are  oval  in  form,  one  in  the  North 
Pacific  between  10°  and  50°  north  latitude, 
one  in  the  North  Atlantic  between  10°  and 
30°  north  latitude,  one  in  the  South  Pacific 
between  5°  and  45°  south  latitude,  one  in  the 
South  Atlantic  between  0°  and  40°  south 
latitude,  and  one  in  the  Indian  Ocean  between 
0°  and  40°  south  latitude.  The  greatest  of 
these  are  the  Pacific  currents.  In  the  far 
south   is   an  Antarctic   current  flowing  from 


182     THE   FITNESS  OF  THE  ENVIRONMENT 

west  to  east;  in  the  north  a  current  flows 
from  east  to  west,  from  the  Siberian  coast 
to  Northeast  Greenland  and  thence  along  the 
east  coast;  another  flows  from  Bafiin's  Bay 
along  the  east  coast  of  North  America. 

Of  all  ocean  currents,  the  Gulf  Stream,  a 
branch  of  the  northern  equatorial  current, 
has  been  most  carefully  studied.  Its  maxi- 
mum velocity  is  220  kilometers  per  day, 
greater  therefore  than  that  of  the  Rhine  at 
Coblentz;  the  mean  about  134  kilometers  a 
day.  In  the  Straits  of  Yucatan  the  Gulf 
Stream  carries  0.2  cubic  kilometer  (200,000,- 
000  tons)  per  second.  If  all  this  water  were 
to  be  cooled  to  the  temperature  of  the  polar 
ocean  this  would  be  equivalent  to  the  trans- 
port of  about  5,000,000,000,000,000  gram 
calories  per  second.  The  magnitude  of  this 
quantity,  of  course,  depends  upon  the  specific 
heat  of  water. 

In  this  manner  vast  quantities  of  water, 
carrying  enormous  stores  of  heat,  are  constantly 
in  motion  all  over  the  globe.  The  result  is 
that  homogeneity  of  the  ocean  which  has  been 
discussed  above,  —  constancy  of  concentra- 
tion, of  composition,  of  temperature,  of  alka- 
linity, and  of  osmotic  pressure. 


THE  OCEAN  183 

III 
THE  OCEAN  AS  ENVIRONMENT 

There  are,  in  accordance  with  our  funda- 
mental postulates  of  the  characteristics  of 
life,  two  principal  requirements  of  the  living 
organism  which  an  environment  must  ful- 
fill, —  such  a  supply  of  matter  and  energy 
for  food  as  may  be  suitable  to  a  complex 
mechanism,  and  stability  of  conditions. 

After  a  general  review  of  the  chief  character- 
istics of  the  ocean,  it  is  therefore  necessary  to 
examine  them  more  particularly  in  relation  to 
such  requirements.  In  so  doing  it  must  not 
be  forgotten,  however,  that  these  characteristics 
of  the  ocean  which  we  have  just  discussed  are 
only  in  part  due  to  the  unique  physical  proper- 
ties of  water  which  have  been  already  dis- 
cussed in  Chapter  III,  and  to  those  of  carbonic 
acid  which  have  been  discussed  in  Chapter 
IV.  In  part  they  depend  upon  the  mere 
magnitude  of  the  sea,  on  the  stability  of  the 
solar  system  and  the  consequent  antiquity  of 
the  geological  and  meteorological  processes, 
and  upon  a  great  variety  of  astronomical  and 
geophysical  conditions.  However,  we  shall 
only  a  little  extend  the  scope  of  our  inquiry 
if  we  now  consider  water  not  only  as  an  indi- 


184     THE   FITNESS  OF  THE   ENVIRONMENT 

vidual  chemical  substance,  that  is  to  say  ab- 
stractly, but  also  naturally,  as  automatic 
processes  of  cosmic  and  geological  evolution 
have  fashioned  it  into  the  principal  constit- 
uent of  the  face  of  the  globe.  Primarily, 
at  any  rate,  the  outcome  of  such  processes  is 
dependent  upon  the  inherent  properties  of 
water  and  upon  the  quantity  of  it  which  is 
present  on  the  surface  of  the  earth,  and  the 
subject  is  too  important  to  be  passed  com- 
pletely by. 

Perhaps  the  first  desideratum  in  an  en- 
vironment as  a  source  of  food  is  mobility. 
Any  organism  which,  like  the  lilies  of  the  field, 
need  not  toil  for  its  nourishment,  is  in  most 
favorable  conditions,  and  such  conditions 
are  the  principal  cause  of  the  enormous  Avealth 
of  vegetation  upon  the  earth.  Now  the  ocean, 
apart  from  the  flora  and  fauna  which  inhabit  it, 
is  perfectly  homogeneous ;  hence  its  mobility 
brings  to  an  organism  all  that  it  has  to  offer, 
and  even  sweeps  along  organic  nourishment 
as  well.  In  the  ocean  not  only  plants  but 
many  animals  may  remain  motionless  and, 
like  the  oyster,  await  the  food  that  will  surely 
be  borne  to  them ;  or  they  may  float  freely, 
relying  on  the  mixing  of  the  water  to  bring 
them  into  contact  with  their  food. 

After    mobility,    richness    and    variety    of 


THE  OCEAN  185 

environment  are  important.  It  is  certainly 
impossible  to  imagine  a  medium  more  rich  and 
varied  in  elementary  constituents  than  sea 
water,  unless  it  be  sea  water  with  still  other  sub- 
stances added  to  it.  But,  in  the  first  place, 
there  are  few  absent  elements  which  might 
be  added,  and,  in  the  second  place,  the  addition 
of  other  substances  would  be  likely  to  cause 
the  escape  of  bodies  which  are  present.  At 
all  events,  the  ocean  is  certainly  more  favor- 
able in  these  three  respects  than  if  it  were 
anything  else  that  could  occur  in  the  course 
of  nature.  Almost  ideally  mobile,  rich,  and 
varied,  the  sea  is  an  almost  perfect  source  of 
supply  for  a  complex  mechanism.  To  be 
sure  there  are  great  difficulties  in  extracting 
its  constituents  from  sea  water,  and  the 
efficiency  of  physiological  processes  is  a  factor 
essential  to  their  utilization,  but  at  least 
there  stand  materials  ready  for  the  mechanism 
which  can  employ  them. 

The  predominance  of  water,  no  doubt,  forces 
that  substance  upon  living  beings  as  their 
chief  constituent;  in  view  of  the  fitness  of 
water  for  the  purpose  that  is  in  itself  a  favor- 
able circumstance.  Otherwise  the  organism 
is  left  free  to  choose  from  all  the  common 
elements,  and  from  some  of  the  rare  ones,  what 
may  be  most  suitable  to  its  purposes  at  every 


186     THE  FITNESS  OF  THE  ENVIRONMENT 

stage  of  the  infinitely  varied  process  of  organic 
evolution.  As  a  result  we  find  here  and  there 
in  the  marine  flora  and  fauna  almost  every 
element  which  the  sea  affords  concentrated 
and  put  to  use. 

After  what  has  gone  before  it  will  not  be 
necessary  further  to  discuss  the  second  great 
qualification  of  an  environment  —  stability 
of  conditions  in  the  ocean.  The  principal 
physical  conditions  and  chemical  compounds 
therein  are  constant ;  that  is  the  whole  case. 
But  it  is  a  case  which  cannot  be  bettered. 
Certainly  nowhere  else  where  life  is  possible, 
probably  in  no  other  place  in  the  universe 
except  another  ocean,  are  so  many  conditions 
so  stable  and  so  enduring. 

The  regulatory  devices  of  our  modern  labo- 
ratories have  not  yet  succeeded  in  rivaling 
the  ocean.  Singly,  certain  conditions,  for 
example,  temperature,  alkalinity,  and  concen- 
tration, may  be  more  accurately  regulated  by 
man,  though  on  a  small  scale  only ;  but  the 
regulation  of  all  such  properties  together  is 
not  yet  possible.  The  only  known  improve- 
ment upon  the  ocean  is  the  body  of  a  higher 
warm-blooded  animal.  Here,  however,  the 
processes  of  organic  evolution  have  begun 
with  the  ocean,  and  in  several  respects  merely 
perfected  existing  arrangements. 


THE  OCEAN 


187 


This  statement  is  far  from  fanciful.  Not 
only  do  the  body  fluids  of  the  lower  forms  of 
marine  life  correspond  exactly  with  sea  water 
in  their  composition,  but  there  are  at  least 
strong  indications  that  the  fluids  of  the  highest 
animals  are  really  descended  from  sea  water, 
from  the  sea  water  of  an  earlier  epoch,  to  be 
sure,  and  they  are  not  changed  beyond  recog- 
nition by  the  transformations  of  evolution.^ 
A  comparison  of  the  relative  amounts  of 
various  saline  constituents  in  sea  water  and 
in  mammalian  blood  (roughly  averaged  from 
a  variety  of  measurements  in  different  species) 
will  demonstrate  this  relationship. 

Composition  of  the  Salts  in  Per  Cent 


Sea  Water 

Blood  Serum 

Na 

30.59 
3.79 
1.20 
1.11 

55.27 
7.66 
0.21 
0.19 

39 

Mg 

Ca       

0.4 
1 

K        

2  7 

CI        

45 

SO4 

CO3 

12 

Br        

P2O5 

0  4 

^  See  the  interesting  paper  by  Macallum,  Transactions  of 
the  Royal  Society  of  Canada,  1908,  II,  p.  145. 


188     THE  FITNESS   OF  THE  ENVIRONMENT 

The  gaps  in  the  table  do  not  indicate  that 
substances  are  lacking,  but  merely  that  the 
amounts  are  small.  In  short,  the  same  sub- 
stances are  present  in  both  cases,  and  in  both 
cases  sodium  chloride  largely  predominates. 
The  importance  of  carbonic  acid  in  metabo- 
lism accounts  for  the  large  amount  of  sodium 
bicarbonate  in  the  blood,  and  this  raises  the 
amounts  of  both  sodium  and  carbonic  acid. 

It  is  also  to  be  noted  that  the  regulatory 
processes  in  the  ocean  and  in  the  organism 
are  in  one  or  two  aspects  similar,  e.g.  tempera- 
ture regulation  by  evaporation,  and  regula- 
tion of  the  alkalinity.  Of  course  no  impor- 
tance attaches  to  such  resemblances,  beyond 
the  fact  that  both  regulations  are  highly 
favorable,  because  of  the  special  fitness  of 
water  in  one  case  and  of  carbonic  acid  in  the 
other.  But  it  is  at  least  worthy  of  mention 
that  the  regulation  of  the  ocean  in  general 
bears  a  striking  resemblance  to  a  physiolog- 
ical regulatory  process,  although  such  physi- 
ological processes  are  supposed  to  be  the 
result  of  organic  evolution  alone.  Very  much 
this  same  idea  occurred  to  Palitzsch  in  the 
course  of  his  investigation  of  the  alkalinity 
of  the  ocean. ^  The  resemblance  is  more  ob- 
vious still  when  the  stability  of  all  the  more 

^  See  note  above,  p.  153. 


THE  OCEAN  189 

important  physical  conditions  of  the  ocean  is 
taken  into  account.  Indeed,  however  difficult 
it  may  be  to  make  out  those  subtle  traits  of 
physiological  processes  which  account  for 
their  efficiency,  their  adaptability,  and  their 
exactness,  I  feel  sure  that  no  one  who  is  thor- 
oughly conversant  with  the  general  char- 
acteristics of  the  life  process  can  fail  to  see  a 
rough  counterpart  in  the  means  by  which 
conditions  in  the  ocean  are  regulated. 

It  is  certainly  a  salient,  and  hardly  a  mean- 
ingless fact  that  the  processes  of  inorganic 
and  organic  evolution  have  a  similar  out- 
come in  complex,  exact,  and  almost  ideally 
efficient  activities.  Is  it  not  possible  that  in 
the  case  of  the  organic  processes  some  have 
now  and  then  been  regarded  as  adaptations 
which  in  reality  arose  automatically  and 
quite  inevitably  .^ 

The  existence  of  efficient  regulation  of  the 
ocean,  establishing  its  most  important  physico- 
chemical  characteristics  as  constants,  is  of 
far  greater  importance  in  the  sciences  of  nature, 
especially  for  living  organisms,  than  could 
formerly  have  been  guessed.  Such  natural 
processes  were  perhaps  even  necessary  to 
make  life  possible  in  the  birthplace  of  life.  I 
cannot  undertake  to  explain  the  very  great 
importance  which  to-day  the  physical  chemist 


190     THE   FITNESS  OF  THE  ENVIRONMENT 

attaches  to  the  regulation  of  the  conditions  of  a 
chemical  process.  The  only  way  to  gain  an 
idea  of  this  is  to  examine  a  work  on  physi- 
cal chemistry.  Certainly,  however,  nothing  has 
lately  arisen  more  essential  to  biology  than  the 
understanding  of  the  influence  of  temperature, 
pressure,  reaction,  concentration,  ionization, 
etc.,  upon  all  physico-chemical  structures 
and  changes,  whether  inorganic  or  vital. 

Thus  the  fitness  of  the  ocean  appears  as  an 
embodiment  of  the  physical  fitnesses  of  water 
and  carbonic  acid,  resulting  directly  and  in- 
evitably from  these  and  other  natural  phenom- 
ena, and  providing  a  lodgment  for  life  and  a 
medium  for  its  earlier  development  upon  the 
earth.  No  philosopher's  or  poet's  fancy,  no 
myth  of  a  primitive  people  has  ever  exag- 
gerated the  importance,  the  usefulness,  and 
above  all  the  marvelous  beneficence  of  the 
ocean  for  the  community  of  living  things. 


CHAPTER  VI 

THE   CHEMISTRY  OF  THE  THREE 
ELEMENTS 


ORGANIC   CHEMISTRY 

A  HUNDRED  years  ago  the  firm  belief 
was  held  by  all  chemists  that  whatever 
substance  is  synthesized  within  the  body  of 
the  living  organism  possesses  special  and  pe- 
culiar characteristics  of  its  own,  which  mark 
it  off  from  all  inorganic  bodies,  and  divide 
chemistry  into  the  two  great  and  perfectly 
distinct  departments  of  Organic  Chemistry 
and  Inorganic  Chemistry.  To  be  sure,  even 
then  many  organic  substances  had  been  sep- 
arated from  the  organism,  purified,  and  sub- 
jected to  the  usual  experiments  of  the  labora- 
tory, without  at  any  stage  manifesting  unique 
properties.  But,  as  Berzelius  believed,  a 
special  vital  force  had  presided  over  their 
formation,  and  this,  therefore,  he  supposed 
to  be  impossible  under  any  other  circum- 
stances. 

191 


192     THE   FITNESS  OF  THE  ENVIRONMENT 

In  the  course  of  time,  however,  a  long  series 
of  successful  syntheses  of  undoubted  constitu- 
ents of  animals  and  plants,  among  which  Woh- 
ler's  preparation  of  urea  in  1828  is  the  most 
famous,  completely  destroyed  the  old  erro- 
neous assumption.  The  compounds  of  organic 
chemistry  gradually  came  to  be  recognized 
as  different  from  inorganic  substances  only 
in  the  special  characteristics  of  the  elements 
carbon,  hydrogen,  and  oxygen  when  in  chem- 
ical union  with  one  another,  just  as  the  com- 
pounds of  any  other  elements  have  their  own 
specific  characteristics.  No  other  difference 
remains ;  every  principle  of  chemical  science 
applies  to  organic  and  inorganic  substances 
alike;  and  accordingly  life  has  been  for- 
ever subjected  to  the  general  laws  of  chem- 
istry. 

As  syntheses  multiplied,  the  organic  chem- 
ist found  many  fields  for  investigation  where 
life  was  not  concerned.  The  application  of 
his  new  substances  in  the  arts,  as  well  as  many 
fascinating  theoretical  problems,  led  him  on, 
until,  about  the  middle  of  the  century  or  a 
little  later,  it  became  clear  that  organic  sub- 
stances in  the  original  sense  are  but  a  small 
part  of  his  scope.  His  occupation  had  be- 
come the  study  of  all  the  compounds  of 
carbon,    wherever   and   however   they   might 


CHEMISTRY  193 

occur,  and  as  a  rule  he  had  httle  to  do  with 
physiological  or  biological  chemistry.  Not 
that  he  was  now  ever  disposed  to  distinguish 
between  substances  which  happened  to  occur 
in  living  organisms  and  others ;  for  at  length 
he  had  completely  accepted  the  view  that, 
apart  possibly  from  a  few  complicated  sub- 
stances like  the  proteins,  such  distinctions 
are  thoroughly  irrational.  But  the  nature  of 
the  subject  and  the  historical  accidents  of 
its  development  directed  his  attention  in  the 
main  elsewhere. 

Nevertheless,  the  distinction  between  or- 
ganic chemistry  as  the  science  of  all  the  com- 
pounds of  carbon,  and  inorganic  chemistry 
as  the  science  of  all  other  chemical  compounds 
whatever  has  persisted,  and  not  without 
sound  reasons.  In  the  course  of  the  wonder- 
ful development  of  organic  chemistry,  which 
must  ever  be  counted  as  one  of  the  greatest 
achievements  of  the  nineteenth  century,  enor- 
mous numbers  of  new  chemical  substances 
were  discovered.  In  1883  the  number  of 
carbon  compounds  had  reached  20,000,  in 
1899,  74,000,  and  in  1902  it  exceeded  100,000.^ 

^  See  M.  M.  Richter,  "Lexikon  der  Kohlenstoffverbindun- 
gen,"  Hamburg  and  Leipzig,  1900,  continued  in  supplemen- 
tary volumes.  This  work  catalogues  all  the  compounds  of 
carbon  as  they  come  to  light. 


194     THE  FITNESS  OF  THE  ENVIRONMENT 

This  is  the  sufficient  practical  ground  for  pre- 
serving organic  chemistry  as  a  separate  sci- 
ence. The  subject  is  so  vast  that  in  fact  it 
is  impossible  to  incorporate  it  with  other 
departments  of  chemistry.  Even  the  com- 
pounds of  carbon  and  hydrogen  alone  are 
counted  by  hundreds,  those  of  carbon,  hydro- 
gen, and  oxygen,  by  thousands,  and  the 
number  of  possible  compounds  of  the  three 
elements  is  almost  unlimited. 

The  mere  number  of  organic  compounds  is, 
however,  far  from  constituting  the  only  dis- 
tinction between  the  two  departments  of 
descriptive  chemistry.  The  unique  variety 
of  compounds  containing  carbon,  hydrogen, 
and  oxygen,  and,  in  a  small  proportion  of  cases 
a  few  other  elements  besides,  must  obviously 
rest  upon  the  nature  of  the  elements  them- 
selves, especially  of  course  upon  the  nature  of 
carbon,  upon  the  properties  which  are  pe- 
culiar to  them  and  which  mark  them  off  from 
other  elements,  just  as  the  properties  of 
argon,  of  the  metals  of  the  alkalies,  or  of  the 
halogens  determine  their  own  chemical  be- 
havior. Moreover,  such  characteristics  must 
and  do  contribute  properties  to  the  com- 
pounds of  carbon  which  are  theirs  as  a  class, 
which  distinguish  them  from  the  compounds 
of  other  elements  in  somewhat  the  same  way 


CHEMISTRY  195 

that  the  anatomical  characteristics  of  one 
class  of  animals  distinguish  such  a  class  from 
other  classes  of  animals.  In  short,  the  carbon 
compounds  are  not  unique  merely  because 
they  are  numerous ;  they  are  uniquely  nu- 
merous because  they  are  compounds  of  carbon 
with  hydrogen,  oxygen,  and  in  some  cases 
certain  other  elements.  They  possess,  more- 
over, other  less  obvious  class  properties  as 
well,  though  of  these,  it  must  be  admitted, 
chemistry  is  even  yet  far  from  a  clear  under- 
standing. But  unquestionably  that  is  due 
to  the  incompleteness  of  the  science,  for  the 
peculiar  methods  of  organic  chemistry  are  a 
sufficient  guarantee  of  the  existence  of  such 
class  peculiarities.^ 

In  our  present  investigation  a  study  of  the 
possibilities  of  chemical  union  between  the 
elements  carbon,  hydrogen,  and  oxygen  is  of 
great  importance,  and  accordingly  we  must 
now  examine  some  of  the  results  of  synthetic 
organic  chemistry. 

^  See  the  introductory  chapter  to  Meyer  and  Jacobson's 
"Lehrbuch  der  Organischen  Chemie,"  Leipzig,  1907. 


196      THE   FITNESS  OF  THE  ENVIRONMENT 


VALENCE 

The  principal  theoretical  foundation  of 
organic  chemistry  is  the  idea  of  valence. 
Let  us  consider  the  chemical  formulas  of  a 
number  of  the  simple  compounds  of  hydrogen, 
e.g.  HCl,  H2O,  NH3,  CH4,  HI,  HBr.  It  is 
evident  that  in  such  formulas  a  single  atom  of 
hydrogen  is  never  represented  as  in  union 
with  more  than  one  atom  of  another  element. 
There  are,  however,  cases  where  one  atom  of 
hydrogen  is  in  union  with  a  single  other  atom, 
e.g.  HCl,  HBr,  HI;  or  two  atoms  of  hydro- 
gen may  unite  with  a  single  other  atom,  e.g. 
H2O;  or  three  atoms  of  hydrogen  with  one 
other,  e.g.  NH3 ;  or  four  hydrogens  with  one 
other,  e.g.  CH4.  If  the  assumption  be  made 
that  discrete  bonds  or  forces  take  part  in  the 
union  of  atoms,  hydrogen  must  possess  but  a 
single  such  bond  or  valence.  Otherwise  com- 
pounds of  the  type  X  — H  — X,   X  — H^    ,  or 

of  some  other  type  in  which  one  atom  of 
hydrogen  is  in  union  with  more  than  one  atom 
of  lower  valence,  must  exist,  and  this  is  con- 
trary to  fact. 

We  may,  therefore,  employing  a  dash  to 
represent    valence,    write    the    constitutional 


CHEMISTRY  197 

formulas  of  hydrochloric  acid,  water,  and 
methane,  as  follows  :  — 

H-Cl,   H-O-H,  JJ)>C<JJ 

Accordingly,  oxygen  appears  to  possess  two 
valences  and  carbon  four.  These  conclu- 
sions are  justified  by  an  almost  inconceivable 
wealth  of  experience ;  they  are  the  means  of 
constructing  the  elaborate  constitutional  for- 
mulas which  are  so  necessary  a  part  of  organic 
chemistr}^ ;  and  there  can  be  no  doubt  that 
in  almost  all  the  compounds  with  which  we 
shall  be  concerned  hydrogen  is  invariably 
univalent,  oxygen  bivalent,  and  carbon  quad- 
rivalent. On  this  basis  the  construction  of 
possible  formulas  of  organic  compounds  is 
merely  an  exercise  in  a  somewhat  peculiar 
department   of  mathematics. 

B 

HYDROCARBONS 

The  compounds  of  carbon  and  hydrogen 
may  first  be  considered.  With  but  a  single 
atom  of  carbon  in  the  molecule  one  only  is 

possible :  — 

H 

I 

H-C-H 

I 

H 


198     THE   FITNESS  OF  THE  ENVIRONMENT 

Uniting  two  carbon  atoms  by  a  single  valence, 
the  formula 

H    H 

I       I 

H-C-C-H 

I       I 

H    H 

representing  the  compound  ethane  is  ob- 
tained ;  but  if  the  process  be  extended,  great 
complexity  speedily  ensues.  For  example, 
the  hexanes,  compounds  formed  upon  this 
plan  containing  six  carbon  atoms,  all  of  one 
empirical  formula,  number  five.  Their  con- 
stitutions are  represented  by  the  accompany- 
ing structures,  every  one  of  which  corre- 
sponds to  a  known  substance  :  — 

H  H  H  H 

I  I  I  I 

H-C-H     H-C-H    H-C-H     H-C-H  H 

H-C-H  C-H 

I  I 

H-C-H  H-C-H  C-H 

I  I  I 

H-C-H  H-C-H  H-C-H 

I  I  I 

H-C-H  H-C-H  H-C-H 

I  I  I 

H-C-H  H  H 

I 
H 


CHEMISTRY  199 

H  H  H  H 

II  II 


H-C-H         H-C-H  H-C-H        H-C-H 


H-C-H        H-C-H 
I 
H 

H-C-H 

I 

H 

In  each  of  the  compounds  represented  by 
these  formulas  every  carbon  atom  is  beheved 
to  have  four  valences  and  every  hydrogen 
atom  one. 

As  the  number  of  carbon  atoms  in  the  mole- 
cule increases  the  number  of  possible  forms, 
isomers  so  called,  multiplies  with  great  rapid- 
ity. Of  compounds  C7H16  there  are  9  forms; 
for  CgHis,  18;  for  C9H20,  35;  for  C10H22,  ^5; 
for  CnH24,  159;  for  C12H26,  355;  for  C13H28, 
802;  and  for  C14H30,  1855  possibilities.^  There 
can  be  no  reasonable  doubt  that  the  prepara- 
tion of  each  and  all  of  these  compounds  would 
be  possible,  and  that  once  formed  they  would 
be  very  stable  substances.     In  truth,  no  one 

1  Cayley,  Berichte,  8,  1056  (1875).  F.  Hermann,  Berichte, 
13,  792  (1880) ;  30,  2423  (1897) ;  31,  91  (1898).  Losanitsch, 
Berichte,  30,  1917,  3059  (1897).  "Optical  isomers"  are  dis- 
regarded in  the  estimate. 


200     THE  FITNESS  OF  THE  ENVIRONMENT 

has  ever  failed  who  has  set  out  with  skill, 
a  good  plan,  and  suitable  starting  materials, 
to  prepare  such  a  body. 

The  number  and  variety  of  hydrocar- 
bons is  further  enormously  extended  by  the 
possibility  of  double  and  treble  unions  be- 
tween pairs  of  carbon  atoms,  as  in  ethylene, 


>'< 


and  acetylene, 

H-C^C-H 

Further,  more  than  one  double  or  treble 
bond,  or  single,  double,  and  treble  bonds  in 
combination,  may  occur,  as  in  the  well-known 
substances  CH3  —  CH  =  CH2,  CH3  —  C  =  CH, 
CH2  =  C  =  CH2,  etc. 

Finally,  the  carbon  atoms  possess  the  prop- 
erty of  uniting  to  form  ring  compounds  in 
great  variety,  e.g. 


H 

H 

CH2 

/\ 

CH2   CH2 

1            1 

C 

HC      CH2 

1        1 

C 

X\ 
HC      CH 

1        II 
HC      CH 

X/ 

c 

H 

1          1           » 

CH2  CH2 

\/ 

CH2 

1        1           > 
HC      CH2 

x/ 

c 

H 

CHEMISTRY  201 

CH2  —  CH2  CH2  —  CH2 

II        ,       \/ 

CH2     CH2  CH2 

\/ 
CH2 


Moreover,  such  rings  may  unite  with  carbon 
chains,  both  those  containing  single  bonds, 
and  those  containing  double  and  treble  bonds, 
whether  straight  or  forked,  in  great  variety ; 
and  also  with  other  rings,  e.g. 


CH3  CH3  CH3 

I  I  I 

c  c  c 

/\  /\  r\ 

HC       CH  H-C       C-CH3  HC       CH 

I        II            ,             I        II               ,  I        II 

HC       CH  HC       CH  HC       C-CH3 

X/  X/  \/ 

c  c  c 

H  H  H 


CH3  CH3 

I  H                                              I 

c  c                               c 

X\  X\       /CHa            yx 

HC      CH  HC      C-CH<                     HC      CH2 

I         II  ,          I        II           ^CH,         ,          I        I 

HC      CH  HC      CH                             HC      CHj 

X/  X/                                        \/ 

C  C                                           CH 

I  H                                            I 

CH3  C 

/X 

CH3    CH2 


202    THE  FITNESS  OF  THE  ENVIRONMENT 

H   H  H  H 

C   C  C     H     C 

HC   C   CH  HC   C  -  C  -  C   CH 

I    II    I        ,        I    11    I    I    II 
HC   C   CH  HC   CH  H  HC   CH 

c    c  c  c 

H      H  H  H 

It  is  quite  impossible  briefly  to  indicate, 
still  less  to  give  an  adequate  idea  of  the 
bewildering  diversity  and  complexity  of  the 
known  hydrocarbons.  They  exist  by  the 
hundreds,  and  there  are  certainly  countless 
thousands  of  possible  stable  bodies  made  up 
of  carbon   and   hydrogen   alone. 


COMPOUNDS  OF  CARBON,  HYDROGEN,  AND  OXYGEN 

With  the  addition  of  oxygen,  the  variety  and 
number  of  known  and  of  possible  substances 
is  still  further  multiplied.  Oxygen  may  enter 
into  the  following  types  of  union  with  carbon 
and  hydrogen  in  organic  compounds  :  — 

=  C-0-H,     ^C-O-C^,     =C  =  0. 

Alone  or  in  combination,  these  groups  yield 
a  great  variety  of  important  classes  of  com- 
pounds. Representing  a  group  or  radical 
consisting  of  carbon  and  hydrogen  alone  by 


CHEMISTRY  203 

R,  a  few  of  the  most  simple  and  important 
divisions  are  as  follows  :  — 


Alcohols, 

primary 

RCH2OH 

Alcohols, 

secondary 

R2CHOH 

Alcohols, 

tertiary 

R3COH 

Aldehydes 

RCHO 

Ketones 

R2CO 

Acids 

RCOOH 

Esters 

RCOOR 

Ethers 

ROR 

By  the  introduction  of  oxygen  into  the 
molecule  any  complex  hydrocarbon  may  be 
converted  into  a  great  number  of  substances, 
and  even  in  simple  cases  such  derivatives 
are  not  few.  In  the  accompanying  formulas 
I  have  gathered  together  the  possible  hydro- 
carbons containing  three  carbon  atoms  (ex- 
cluding ring  compounds),  and  their  possible 
oxygen  derivatives,  most  of  which  are  capa- 
ble of  existence  as  substances  of  varying 
stability,  many  of  them  being  in  fact  well- 
known  common  substances  like  lactic  acid, 
glycerine,  propionic  acid,  propyl  alcohol,  two 
of  the  simplest  sugars,  etc. 

CH3  CH3  CH2  CH3 

I  I  11  I 

CH2  CH  C  C 

I  il  II  III 

CH3  CH2  CH2  CH 


204     THE   FITNESS  OF  THE  ENVIRONMENT 


CH3 

I 
CH2 

I 
CH2OH 


CH3 

I 
CHOH 

I 
CHs 


CH3 

I 
CH 


CHs 

I 
COH 


CHOH      CH2 


CH2OH     CH2 


I 

CH 
II 
CH2 


II 

C 
II 
CHOH 


CH3 

I 
C 

III 
COH 


CH2OH      CH3 


I 
C 

III 

CH 


CH2OH     CH3 


CHOH       CH, 


I 
COH 


CH2OH 

I 
CH 


CHoOH      CH2OH      CHOH       CHOH 


CH2OH     CHOH      CHoOH     CH2OH      CH2OH 


1 
COH 

II 
CH2 


CHOH       COH 


I 
CHOH 


I 
COH 

li 


I 
CH2OH      CHOH 


CH3 

I 
CH2 

I 
CHO 


CH3 
1 
CO 

I 
CH3 


CH3 

I 

CH 

II 
CO 


CHO 

I 
CH 

II 
CH2 


CO 

II 

c 
II 
CH2 


CHO 

1 

c 

III 

CH 


CH3 
1 
CO 

1 

CHO 


CHO 
! 

CH2 
I 
CHO 


CHO 

I 
CH 

II 
CO 


CO 

II 
c 

11 

CO 


CHO 

I 
CO 

I 

CHO 


CH3  COOH 

I  I 

CH2  CH 

I  II 

COOH  CH2 


COOH  COOH 

I  I 

C  CH2 

III  I 

CH  COOH 


CH3 

I 
CHOH 

I 
CHO 


CH2OH 

I 
CH2 

I 
CHO 


CH2OH  CH3 

I  I 

CO  COH 

I 


CH3 


CO 


CH2OH      CHO 


I 

CH 
II 
CO 


I 

COH 

II 
CH2 


CHEMISTRY 

205 

CHO 

1 

CHOH 

II 

c 

II 

CO 

CHO 

1 

CH 

II 
CHOH 

1 

C 
III 
COH 

CH2OH 

1 

CH20H 

1 

CH2OH 

1 

CHO 

1 

CH2OH 

1 

CHO 

1 

CHOH 
1 
CHO 

CO 

1 
CH20H 

COH 

II 
CO 

COH 

II 
CHOH 

CO 

1 

CHO 

CHOH 

1 
CHO 

CHO 

COH 

11 
CO 

CH3 

CH20H 

1 

COOH 

1 

COOH 

1 

COOH 

1 

CH2OH 

1 

CHOH 

1 
COOH 

CH2 

1 

COOH 

COH 

II 
CH2 

CH 

II 
CHOH 

1 

c 

III 

COH 

CHOH 
1 
COOH 

COOH 

1 

COOH 

1 

COH 

II 
CHOH 

CHOH 

1 

COOH 

CH3 

CHO 

1 

COOH 

1 

COOH 

1 

CO 

1 

CH2 

1 

CH 

II 
CO 

CO 

1 

COOH 

COOH 

COOH 

CH2OH 

1 

CHO 

1 

COOH 

1 

CO 

CHOH 

COH 

I  I  II 

COOH       COOH      C  =  O 


206    THE  FITNESS  OF  THE  ENVIRONMENT 

This  is  relatively  a  simple  case.  As  the 
number  of  carbon  atoms  in  the  molecule 
increases,  the  number  of  possible  oxygen 
derivatives  multiplies  in  a  far  more  rapid 
progression  than  in  the  case  of  the  simplest 
hydrocarbons,  which  has  been  stated  above. 
Accordingly  there  can  be  no  doubt  that  in 
addition  to  the  many  thousands  now  known, 
the  existence  of  countless  millions  of  com- 
pounds consisting  of  carbon,  hydrogen,  and 
oxygen  alone  is  possible.  In  a  large  propor- 
tion of  cases  the  only  difficulties  involved  in 
their  preparation  are  to  obtain  suitable  start- 
ing materials,  and  the  enormous  labor  of  the 
process.  There  are,  for  instance,  hundreds 
of  thousands  of  possible  hydroxyl  derivatives 
alone  of  the  paraffine  hydrocarbons  of  the 
formula  C14H30,  but  only  one  of  these  is  now 
known. ^  Yet  all,  or  at  least  a  vast  majority, 
would  unquestionably  be  stable  bodies  if 
once  formed. 

Not  less  important  than  the  number  and 
variety  of  such  substances  is  their  diversity 
of  physical  and  chemical  characteristics.  The 
following  are,  for  example,  individual  chemi- 
cal compounds  of  at  least  moderate  purity, 
made  up  of  the  three  elements  alone:  al- 
cohol,   formaldehyde,    acetic    acid,    carbolic 

^  Methal,  a  constituent  of  spermaceti. 


CHEMISTRY  S07 

acid,  oxalic  acid,  acetone,  ether,  lactic  acid, 
sugar,  cotton,  glycerine,  olive  oil,  camphor, 
tannin,  ophiotoxin  (the  chief  poisonous  con- 
stituent of  cobra  venom),  starch,  vanilline 
(the  flavoring  constituent  of  the  vanilla  bean), 
oil  of  wintergreen,  salol,  benzoic  acid,  digita- 
line. 

Here  is  a  variety  that  baflBes  description; 
but  description  is  hardly  necessary,  for  the 
facts  explain  themselves.  In  short,  the  com- 
pounds of  the  three  elements  which  compose 
water  and  carbon  dioxide  exist  in  enormous 
numbers  and  in  unparalleled  diversity  of  chem- 
ical and  physical  characteristics.  They  in- 
clude substances  of  the  greatest  stability,  and 
others  of  exceeding  instability  ;  liquids,  solids, 
and  gases ;  chemically  active  and  chemically 
inert  bodies;  acids  and  neutral  substances; 
substances  which  are  readily  oxidized  and 
others  which  are  oxidized  only  with  great 
difficulty.  In  a  very  large  proportion  of 
cases  these  compounds  are  capable  of  enter- 
ing into  reactions  with  one  another.  They 
are,  moreover,  capable  of  forming  still  more 
complex  substances,  in  still  greater  variety 
by  entering  into  union  with  other  elements, 
notably  with  nitrogen  and  sulphur. 


208    THE  FITNESS  OF  THE  ENVIRONMENT 

D 
OTHER  ORGANIC   COMPOUNDS 

The  organic  substances  which  contain 
nitrogen  are  very  numerous  and  exceedingly 
diverse  in  their  properties.  A  few  of  the 
principal  classes  of  such  compounds  are  the 
following :  — 

Amines  R-NH2,  R2NH,  R3N 

Nitro  compounds       R  — NO2 
Nitriles  R-C  =  N 

Isonitriles  R-NC 

Amino-acids  R  -  CH  •  NH2  •  COOH 

R-N. 
Azoxy  compounds  I  /O 

R-N^ 
Azo  compounds  R  — N  =  N  — R 

Hydrazo  compounds  R  — NH  — NH  — R 

Derivatives  of  purine,  pyridine,  and  other 
ring  systems,  etc. 

The  nitrogenous  organic  substances  include 
classes  of  compounds  which  differ  in  their 
properties  from  any  of  the  non-nitrogenous 
substances.  Of  such  special  properties  the 
most  conspicuous  is  perhaps  alkalinity.  Like 
ammonia,  of  which  it  is  a  derivative,  the 
amino  group  (—  NH2),  and  various  other 
groups  containing  nitrogen  possess  this  char- 


CHEMISTRY  209 

acteristic.  Such  compounds,  accordingly, 
supplement  those  which  contain  the  acid 
carboxyl  group  ( —  COOH)  and  make  possible 
the  fundamental  relations  of  acid,  base,  and 
salt  among  organic  compounds,  corresponding 
to  those  of  inorganic  chemistry. 

There  exist  also  many  compounds  of  sul- 
phur, of  chlorine,  bromine,  and  iodine,  as 
well  as  of  various  less  common  elements 
among  organic  substances ;  but  in  all  such 
cases  the  complexity  and  variety  of  the 
compounds  depend  primarily  upon  the  ca- 
pacity of  carbon,  hydrogen,  and  oxygen,  or 
carbon  and  hydrogen  together,  to  form  nu- 
merous, varied,  and  complex  compounds  on 
which,  as  it  were,  the  further  complexity  is 
superposed. 

E 
THE  CHARACTERISTICS  OF  ORGANIC  SUBSTANCES 

Thus  the  great  diversity  of  organic  sub- 
stances depends  in  the  first  instance  upon  the 
quadrivalence  of  carbon,  which  makes  of 
the  carbon  atom  in  the  organic  molecule  a 
focus,  from  which  chains  of  atoms  may  ex- 
tend in  four  different  directions ;  or,  in  the 
case  of  double  or  treble  ties,  in  three  directions ; 

t 
or    in    but    two:    <-C->,    /C=>,     <=C=>, 


210     THE  FITNESS  OF  THE  ENVIRONMENT 

<-C=>.  Next  comes  the  fact  that  carbon 
atoms,  when  otherwise  exclusively  in  com- 
bination with  hydrogen,  and  under  other 
circumstances  in  lesser  degree,  possess  an 
almost  unlimited  capacity  to  join  together 
and  form  chains  and  rings  in  great  variety. 
The  longest  carbon  chain  yet  synthesized  oc- 
curs in  the  compound  hexakontane,^  C60H122, 
a  substance  whose  constitution  is  probably  as 
follows :  — 

CH3CH2CH2  CH.  CH.'CH.. 

(CH2)54 

The  stability  of  this  substance  justifies  a 
belief  that  even  far  longer  chains  of  carbon 
atoms  can  exist,  and,  in  fact,  there  is  no  known 
limit  to  the  possibility  of  stringing  carbon 
atoms  together. 

No  other  element  is  believed  to  share  both 
of  these  characteristics,  and  there  are  various 
reasons  to  suppose  that  the  resulting  pecul- 
iarity of  the  system  of  organic  compounds 
is  really  unique.  Turning  to  the  periodic 
classification  of  the  elements,  it  will  be  seen 
that  carbon  is  a  member  of  the  first  series. 
Several  of  the  elements  of  this  series,  unlike 
all  the  other  elements  except  hydrogen,  pos- 
sess very  definite  individual  properties,  which 

1  "  Hell  und  Hagele,"  Berichte,  22,  502  (1899). 


CHEMISTRY  211 

mark  them  off  sharply  from  other  substances. 
Thus  carbon  bears  relatively  little  resem- 
blance to  its  neighbors  silicon  or  titanium, 
nitrogen  to  phosphorus  or  vanadium,  oxy- 
gen to  sulphur  or  chromium ;  while  hydro- 
gen, of  course,  has  a  place  quite  apart  in  the 
classification,  and  as  an  element  appears  to 
be  correspondingly  unique. 

It  is,  therefore,  in  the  highest  degree  prob- 
able that  compounds  made  from  elements  of 
such  positive  chemical  characteristics  and 
very  unusual  properties  will  be  unlike  com- 
pounds formed  from  other  elementary  sub- 
stances. In  this  manner  the  periodic  classi- 
fication confirms  our  confidence  in  the  results 
of  many  decades  of  experience,  which  lead  us 
to  believe  that  other  elements  are  exceedingly 
unlikely  readily  to  form  compounds  com- 
parable in  number,  variety,  and  complexity 
with  those  of  organic  chemistry  as  we  know  it. 

For  more  evidence  we  may  turn  to  certain 
further  data  of  organic  chemistry.  I  refer 
principally  to  the  character  of  the  organic 
radicals  composed  exclusively  of  carbon  and 
hydrogen.  In  making  a  rational  classifica- 
tion of  the  carbon  compounds  it  has  been 
found  convenient  to  commence  with  that 
series  of  hj^drocarbons,  called  paraflfines,  with 
which    the    present    discussion    was    begun. 


212     THE  FITNESS  OF  THE  ENVIRNOMENT 

From  them  other  series  may  be  derived  by 
making  a  substitution  in  the  molecule.  Thus 
the  substitution  of  a  hydroxyl  radical  for  a 
single  hydrogen  atom  leads  from  the  paraf- 
fine  hydrocarbons,  C„H2;,+2,  to  the  alcohols 
C^H2n+iOH ;  the  substitution  of  a  carboxyl 
radical  —  COOH,  for  the  methyl  group  —  CH3, 
leads  from  the  paraffine  hydrocarbons 
C„H2n+i  •  CH3  to  the  acids  C^H2n+rC00H. 

Moreover,  the  classes  of  compounds  thus 
defined  chemically  fulfill  the  logical  require- 
ments of  a  class.  They  are  collections  of 
well-characterized  and  very  similar  individual 
things  which  differ  greatly,  and  in  well-marked 
manner,  from  all  other  things.  In  other 
words,  growing  complexity  of  the  molecule, 
when  it  consists  only  in  increase  in  complexity 
of  the  simple  radical  comprised  of  carbon 
and  hydrogen,  of  the  formula  C„H2n+ij 

CH3 — ,  CH3-CH2 — ,  CH3*CH2*CH2 — ,  CH3-CH2*CH2'CH2 — 
CH3.  CHs. 

^CH-,  p>CH-CH2- 

CH3  CH3 

CH3  —  CH2V 

>CH- 
CW 

CHsN. 

CHs-^C- 
CH3/ 

has  very  little  effect  upon  the  properties  of 
the  molecule.     Thus  the  compound  methane. 


CHEMISTRY  213 

CH4,  very  closely  resembles  normal  butane, 
CH3  •  CH2  *  CH2  •  CH3 ;  and  again  propionic 
acid,  CH3  •  CH2  •  COOH,  and  heptylic  acid, 
CH3  •  CH2  •  CH2  •  CH2  •  CH2  •  CH2  •  COOH,  are 
very  much  alike. 

Quite  different  is  the  case  when  any  other 
radical  accumulates  in  the  molecule.  For 
instance,  propyl  alcohol,  CH3*CH2*CH2*OH, 
which  closely  resembles  ordinary  alcohol, 
CH3*CH20H,  is  very  different  in  its  behavior 
from  glycerine,  CH2OH  CHOH  CH2OH, 
and  similarly,  acetic  acid,  CH3- COOH,  differs 
materially  in  properties  from  oxalic  acid 
COOH -COOH.  Even  more  marked  are  the 
differences  when  a  radical  accumulates  upon 
a  single  carbon  atom.  In  successive  stages 
of  oxidation  ethane,  CH3*CH3,  yields  alcohol, 
CH3CH2OH,  aldehyde,  CH3CH(OH)2,  which 
by  a  secondary  transformation  goes  over  into 
the  more  stable  form  CH3*CH0,  and  acetic 
acid,  CH3-C(OH)3,  which  similarly  becomes 
CH3*C00H.  These  changes  correspond  to 
the  conversion  of  ethane,  that  is  monomethyl 
methane,  into  dimethyl  methane,  trimethyl 
and  tetramethyl  methane  :  — 

CH3-CH3->CH3CH2CH3-> 

CHsX^^       r^TT    _.    CHgX^/CHg 

cuy^    -  ^^3  -^  CHs/^Xcm. 


214      THE  FITNESS  OF  THE  ENVIRONMENT 

In  the  latter  case  the  introduction  of  methyl 
groups  in  place  of  hydrogen  produces  no  appre- 
ciable change  in  the  general  characteristics 
of  the  substances ;  in  the  former,  the  succes- 
sive introduction  of  hydroxyl  groups  forms 
substances  belonging  to  three  different  classes 
of  compounds,  —  alcohols,  aldehydes,  and  acids, 
which  have  nothing  in  common.  In  short, 
variation  in  the  number  and  arrangement  of 
such  groups  as  occur  in  the  paraffine  hydro- 
carbon. 


—  C  —  C-Hs,  — C  —  CIl2  —  C 


I      I 

-C\       /C- 

'V' 

'  /  \ ' 

I         I 

is  without  manifest  effect  upon  the  more 
important  properties  of  the  molecule,  but 
variation  in  the  number  and  arrangement  of 
any  other  groups  produces  complete  change 
in  its  characteristic  properties. 


CHEMISTRY  215 

It  may  perhaps  be  urged  that  this  argu- 
ment is  fallacious,  in  that  the  increase  of  the 
relative  amount  of  hydroxyl  in  the  above 
cases  is  larger  than  the  relative  change  in 
radicals  of  the  types  —  CH3,  =CH2,  =CH, 
and  =  C.  But,  in  the  first  place,  it  is  evi- 
dent that  the  latter  four  radicals  are  actually 
different,  and  a  priori  there  is  no  reason  to 
suppose  that  they  should  not  greatly  differ 
in  their  effect  upon  the  properties  of  a  mole- 
cule, for  instance,  to  render  dissimilar  the 
compounds  normal  pentane  CH3-CH2*CH2* 
CH2'CH3   and  tetramethyl  methane, 

CHaX    /CII3 

CH3/^\CH3, 

which  is  not  the  case.  In  the  second  place, 
the  change  from  methane,  CH4,  to  ethane, 
CH3  •  CH3,  is  a  larger  proportional  change  in 
the  molecule  than  the  change  from  alcohol, 
CH3CH2OH,  to  glycol,  CH2OHCH2OH,  or 
aldehyde,  CH3  •  CHO,  both  of  which  produce 
far  greater  changes  in  the  properties. 

In  fact,  the  union  of  carbon  with  hydrogen 
in  organic  compounds  is  a  unique  and  peculiar 
chemical  relationship,  upon  which  the  proper- 
ties of  the  carbon  compounds,  their  number, 
variety,  and  complexity  largely  depend.  It 
seems  to  make  no  important  difference  whether 


216      THE   FITNESS  OF  THE  ENVIRONMENT 

a  carbon  atom  is  attached  to  four  hydrogen 
atoms,  or  to  one  carbon  and  three  hydrogens, 
or  to  two  carbons  and  two  hydrogens,  or  to 
three  carbons  and  one  hydrogen,  or  to  four 
carbon  atoms ;  in  all  such  cases  the  effect 
of  the  radical  upon  the  general  characteristics 
of  the  molecule  varies  very  little. 

There  are  a  great  number  of  phenomena 
which  might  be  employed  further  to  illustrate 
the  nature  of  the  case,  but  two  will  suffice. 
The  acidity  of  acetic  acid,  CHg-COOH,  is 
only  slightly  and  slowly  changed  by  the 
accumulation  of  hydrocarbon  radicals;  thus 
the  compounds  propionic  acid,  CHa'CHg* 
COOH,  and  butyric  acid,  CHa-CHa-CHs' 
COOH,  are  only  a  little  less  acid  than  acetic 
acid  itself,  because  nearly  all  the  effect  of 
such  larger  radicals  as  they  contain  is  already 
exerted  by  the  methyl  group. 

Ionization  Constants  of  Acids 


Acetic  acid. 

CH3  COOH 

0.000018 

Propionic  acid, 

CH3 .  CHo  COOH 

0.000014 

Butyric  acid, 

CH3  CH2  CH2  COOH 

0.000016 

Glycolic  acid, 

CH2OH  COOH 

0.00015 

Chloracetic  acid, 

CH2CI  COOH 

0.0015 

Dichloracetic  acid, 

CHCI2  COOH 

0.05 

Trichloracetic  acid. 

CCI3  COOH 

1.2 

GlycocoU, 

CH2NH2  COOH 

0.00000000018 

Oxalic  acid. 

COOH  COOH 

0.1 

CHEMISTRY  217 

But  if  a  hydroxyl  group  be  substituted,  as  in 
glycolic  acid,  CH20H-C00H,  or  a  chlorine 
atom,  as  in  monochloracetic  acid,  CH2C1* 
COOH,  the  acidity  is  greatly  increased,  while 
the  compound  trichloracetic  acid,  CCla- 
COOH,  is  a  strong  acid.  On  the  other  hand, 
aminoacetic  acid,  CH2*NH2*COOH,  is 
scarcely  acid  at  all. 

The  effect  of  introducing  a  carboxyl  group 
in  place  of  a  methyl  group  into  any  paraflSne 
hydrocarbon,  regardless  of  its  constitution, 
e,g,  CHa-CHa-^CHs-COOH,  is  to  diminish 
the  heat  of  combustion  of  the  molecule  almost 
exactly  157  calories ;  but  the  conversion  of 
acetic  acid  into  oxalic  acid,  CH3*C00H-> 
COOH -COOH,  structurally  an  identical 
change,  diminishes  the  molecular  heat  of 
combustion  only  147  calories.^  In  both  these 
instances  it  is  certain  that  the  nature  of  the 
influence  of  the  radicals  consisting  of  carbon 
and  hydrogen  exclusively  is  nearly  independ- 
ent of  their  size  and  configuration.  Any 
other  group,  however,  by  its  presence  at  once 
modifies  the  nature  of  the  case,  though  un- 
concerned in  the  process  or  property.  Since 
it  can  be  shown  that  such  effects,  like  the 
difference  between   monochloracetic  acid  and 

*  Stohmann,  Zeitschrift  fiir  Physikalische  Chemie.  11,  29, 
1888. 


218     THE  FITNESS  OF  THE  ENVIRONMENT 

trichloracetic  acid,  depend  upon. the  number 
of  such  foreign  groups  and  their  arrangement/ 
it  is  evident  that  the  hydrocarbon  radicals 
have  a  constancy  of  influence  upon  the  prop- 
erties of  the  molecule  which  is  not  shared  by 
other  radicals. 

The  indifference  of  effect  of  hydrogen  and 
carbon,  when  linked  to  carbon,  upon  the 
properties  of  the  molecule  is  undoubtedly  a 
principal  cause  of  the  stability  of  complex 
organic  substances.  Through  this  peculiar- 
ity of  the  two  elements  the  integrity  of  the 
valence  energy  of  carbon  is  preserved,  and  the 
long  carbon  chains  are  stable.  Whenever 
the  molecule  becomes  overloaded  with  radi- 
cals of  other  kinds  the  strength  of  the  tie 
between  carbon  atoms  diminishes  and  the 
compound  becomes  unstable.  The  proper- 
ties of  the  carbohydrates,  which  will  be  later 
discussed,  admirably  illustrate  such  instabil- 
ity. In  short,  organic  compounds  are  in  some 
respects  properly  to  be  regarded  as  compounds 
of  carbon  and  hydrogen  jointly,  for  it  is  not 
the  properties  of  carbon  alone,  but  those  of 
carbon  and  hydrogen  together  which  chiefly 
make  them  possible. 

^  Henderson,  Journal  of  Physical  Chemistry,  IX,  40,  1905  ; 
Proceedings  of  the  American  Academy  of  Arts  and  Sciences, 
XLII,  639,  1907 ;  Zeitschrift  fiir  Physikalische  Chemie,  LX, 
413,  1907. 


CHEMISTRY  219 

In  the  more  complex  substances,  such  as 
the  various  ring  systems  of  organic  chemistry, 
it  is  not  possible  to  discuss  such  problems  of 
molecular  mechanics.  There  too,  however, 
hydrogen  predominates  over  all  other  elements 
except  carbon,  and  that  may  well  be  taken  as 
a  sufficient  indication  of  its  continued  im- 
portance. 

All  of  these  considerations  taken  together 
suffice,  I  believe,  to  prove,  or  at  least  to  make 
it  exceedingly  probable,  that  organic  chemistry 
is  in  truth  a  unique  field,  and  that  no  other 
elements  can  form  compounds  in  such  variety, 
complexity,  and  number  as  carbon,  hydrogen, 
and  oxygen.  At  any  rate  there  can  be  no 
possible  doubt  that  the  compounds  of  organic 
chemistry  are  in  these  respects  very  remark- 
able indeed,  and  that  similar  cases  must  be 
extremely  rare  among  all  the  possible  systems 
of  compounds  made  up  of  all  the  known 
elements. 

It  follows  from  the  peculiarities  just  ex- 
plained that  the  first  great  factor  in  the  com- 
plexity of  living  organisms  as  we  know  them, 
the  complexity  and  variety  of  their  chemical 
constituents,  depends  principally  upon  the 
nature  of  the  elements  which  compose  such 
substances,  and  is  most  probably  a  unique, 
certainly  a  very  rare  characteristic  of  matter. 


220     THE  FITNESS  OF  THE  ENVIRONMENT 

That  the  very  elements  which  make  up  water 
and  carbonic  acid,  and  apparently  they  alone, 
should  possess  this  wonderful  property  is, 
when  taken  together  with  the  physical  prop- 
erties of  water  and  carbonic  acid  and  their 
place  in  cosmic  evolution  as  constituents  of 
the  atmosphere,  a  fact  which  cannot  lightly 
be  set  aside. 

Not  less  valuable  for  the  organism  than  the 
multiplicity  of  organic  substances,  and  the 
diversity  of  their  properties,  are  the  great 
variety  of  chemical  changes  which  they  can 
undergo,  and  that  characteristic  instability 
which  renders  such  great  complexity  of  chem- 
ical behavior  easily  attainable.  In  short, 
organic  substances  are  uniquely  fitted  not 
only  to  provide  complexity  of  structure  to  the 
organism,  but  also,  through  their  instability 
and  manifold  transformations,  to  endow  it 
with  diverse  chemical  activities,  with  com- 
plexity of  physiological  function. 

One  factor  in  determining  the  complexity 
of  chemical  changes  which  organic  chemical 
substances  manifest  is  the  enormous  number 
of  simple  structural  relationships  which  every 
substance  bears  to  others.  This  may  be 
readily  illustrated  by  the  formulas  of  some  of 
the  derivatives  of  propane  which  possess 
biological  importance :  — 


CH3 

I 
CH2 

I 
CH2OH 


CHEMISTRY 
CH3 


CH2 
COOH 


CH3 

I 
CO 

I 
CH3 


221 


CH3 

I 
CO 

I 

CHO 


Propyl  alcohol,     Propionic  acid,     Acetone,     Methyl  glyoxal. 


CH3 

CHOH 

I 
COOH 

Lactic  acid, 


CH2OH 

I 
CHOH 

I 
CH2OH 

Glycerine 


CH2OH 

CHOH 

I 
CHO 

Glycerine 

aldehyde, 


CHoOH 

I 
CO 

I 

CH20H 

Dioxyacetone 


CH3 

I 
CH  NH2 

I 
COOH 


Alanine, 


CH2OH 

I 
CH  NH2 

I 
COOH 

Serine, 


CH2  •  SH  CH3 

I  I 

CH  NH2  CH  SH 

I  I 

COOH  COOH 

Cysteine,  a-Thiolactic 

acid 


Of  the  above  substances,  acetone,  lactic  acid, 
glycerine,  glycerine  aldehyde,  dioxyacetone, 
alanine,  serine,  and  cysteine  are  of  the  great- 
est moment  in  physiological  processes. 

Such  complexity  of  chemical  relationships 
results  automatically,  so  to  speak,  in  a  variety 
of  chemical  transformations.  But  the  trans- 
formations are  greatly  facilitated  by  that 
characteristic  instability  of  organic  substances, 
which  is  perhaps  the  chief  distinguishing  fea- 
ture of  their  behavior.  For  example,  many 
inorganic  substances  may  be  subjected  to  very 


222    THE  FITNESS  OF  THE  ENVIRONJVIENT 

high  temperatures  without  undergoing  chem- 
ical change,  but  there  are  hardly  an}^  organic 
substances  which  can  survive  such  treatment. 
Organic  substances  are  also  peculiarly  liable 
to  modification  from  the  action  of  light  and 
air.  These  are,  however,  but  rough  indica- 
tions of  instability,  and  a  special  case  will  help 
more  clearly  to  define  the  real  characteristic. 

F 

THE  SUGARS 

In  accordance  with  the  researches  of  Emil 
Fischer,  the  following  constitution  is  ordina- 
rily assigned  to  glucose.^ 

H 

I 

C  =  0 

I 
H-C-O-H 

I 
H-O-C-H 

I 
H-C-O-H 

I 
H-C-O-H 

I 

CH2OH 

*  A  discussion  of  this  formula  may  be  found  in  any  text- 
book of  organic  chemistry. 


CHEMISTRY  223 

It  must  be  noted  that  carbon  atoms  to 
which  four  different  groups  are  attached  are 
asymmetric,  that  is  to  say,  they  can  exist  in 
two  forms  which  resemble  each  other  as  the 
right  hand  resembles  the  left  (Pasteur,  LeBel, 
van't  Hoff).  This  characteristic  results  in 
further  increase  in  the  number  and  variety  of 
organic  compounds.  It  is  therefore  neces- 
sary, in  writing  the  formula,  to  represent  the 
form  of  the  molecule  as  it  exists  in  space  (in 
three  dimensions),  and  this  is  actually  accom- 
plished by  imagining  the  three-dimensional 
formula  to  be  projected  upon  the  paper  so  that 
when  the  hydrogen  atom  is  written  to  the  right 
of  the  carbon  atom  one  asymmetric  form  of 
the  latter  is  designated,  when  the  hydrogen 
atom  appears  to  the  left,  the  other. 

It  has  long  been  known  that  when  glucose 
is  dissolved  in  water  its  optical  activity,  as 
the  power  of  a  substance  to  rotate  the  plane 
of  polarization  of  light  is  loosely  termed, 
changes  slowly  for  some  time  before  reaching 
a  constant  value.  Recently  it  has  been  shown 
that  this  phenomenon  probably  depends  upon 
the  existence  in  solution  of  three  different  forms 
of  glucose,  which  pass  freely  into  one  another 
and  ultimately  attain  a  state  of  equilibrium.^ 

^  This  subject  has  been  fully  discussed  by  Hudson,  Journal 
of  the  American  Chemical  Society,  XXXII,  889,  1910. 


224     THE  FITNESS  OE  THE  ENVIRONMENT 


OH 
I 
H-C— 


I 
H-C-OH 
I  O 

HO-C-H 


H-C 

I 
H-C-OH 
I 
CHoOH 


CHO 

I 
H-C-OH 

I 
:^    HO-C-H 

I 
H-C-OH 

I 
H-C-OH 


I 
CHoOH 


H 

I 
HO-C 


H 


OH 


C 

I  O 

HO-C-H 
I 
H-C 


H-C-OH 
I 
CHoOH 


When  to  such  a  solution  of  glucose  a  small 
quantity  of  alkali  is  added,  certain  remarkable 
further  changes  occur,  as  was  first  demon- 
strated by  Lobry  de  Bruyn.^  These  pro- 
cesses result  in  the  formation  of  mannose  and 
levulose,  probably  according  to  the  accom- 
panying diagram. 

Moreover,  like  glucose,  levulose  and  man- 
nose  both  exist  in  solution  in  three  different 
forms,  so  that  the  resulting  solution  contains 
at  least  ten  chemical  individuals.  But  it  is 
almost  certain  that  other  changes  simultane- 
ously occur  and  that  the  solution  is  actually 
still  more  complex,  even  from  the  outset. 

Upon  a  continued  increase  of  alkalinity, 
or  even  slowly  under  the  original  conditions, 
a  multitude  of  other  changes  set  in.     These 

^  See  the  numerous  papers  by  Lobry  de  Bruyn  and  Al- 
berda  van  Eckenstein  in  Recueil  des  Travaux  Chimiques 
des  Pays  Bos,  XIV-XIX. 


CHEMISTRY  225 

CHO 

I 
HCOH 

I 
HOCH 

I 
HCOH 

I 
HCOH 

I 

CH2OH 


I 


CH2OH  CHOH  CHO 

I  II  I 

CO  C-OH  HO-C-H 

I  I  1 
HO-C-H       :?^     HO-C-H       ^      HO-C-H 

I  I  I 

H-C-OH  H-C-OH  H-C-OH 

I  I  I 

H-C-OH  H-C-OH  H-C-OH 

I  I  I 

CH2OH  CH2OH  CH2OH 

Levulose  Mannose 


are  known  sometimes  to  lead  to  the  formation 
of  lactic  acid,  CHa-CHOH-COOH,  methyl- 
glyoxal,  CHs'CO-CHO,  and  formaldeh^^de, 
H-CHO.  Further,  as  Neff  has  shown, ^  many 
other  substances  may  also  be  formed.  Such 
bodies  chiefly  belong  to  the  class  of  oxyacids. 
It  is  also  certain  that  a  great  variety  of  other 
simple    sugars    resembling    glucose,    levulose, 

1  Neff,    "Liebig's   Annallen,"   376,   p.  1,  1910,   and  357, 
p.  294,  1907. 


226     THE  FITNESS  OF  THE  ENVIRONMENT 

and  mannose  are  produced,  and,  all  told,  the 
constituents  of  such  a  solution  probably 
number  at  least  two  hundred,  all  produced 
from  glucose  alone,  under  the  influence  of  a 
slight  excess  of  hydroxyl  ions.  Among  these 
substances  the  greatest  diversity  of  chemical 
behavior  is  to  be  distinguished.  Alcohol, 
aldehyde  and  ketone,  and  acid  radicals  occur 
in  great  profusion  and  variety  of  combinations  ; 
compounds  possessing  forked  chains  are  pres- 
ent ;  and  double  bonds  between  carbon  atoms 
add  to  the  complexity.  Moreover,  all  these 
substances  themselves  possess  great  chemical 
activity. 

A  single  case  may  perhaps  illustrate  this 
point.  It  has  been  shown  by  Windaus  and 
Knoop  ^  that  in  such  solutions,  in  the  presence 
of  ammonia,  one  molecule  of  methyl  glyoxal, 
one  of  formaldehyde,  and  two  of  ammonia 
unite  to  form  the  cyclic  compound,  methyl 
imidazol,  a  substance  related  to  histidine, 
the  latter  being  an  important  constituent  of 
the  protein  molecule  :  — 

CH3— C  =  0      NH3         /H        CH3— C-N/H 

I  C^O  _>  II        \C-H 

C  =  0      NH3         ^  H— C— N^ 


k 


1  Knoop    and  Windaus,   Berichte,   XXXVI,   1166,    1905. 
Hofmeister's  Beitrdge,  VI,  392,  1905. 


CHEMISTRY  227 

The  instability  of  glucose  and  of  all  the 
simple  sugars  is  indeed  exceptional  in  char- 
acter, and  the  resulting  processes  are  perhaps 
far  more  intricate  and  numerous  than  in  any 
other  similar  case.  However,  this  very  case 
is  of  exceptional  physiological  importance,  be- 
cause carbohydrates  are  the  direct  result  of 
that  synthetic  action  of  chlorophyll, 

6  CO2  +  6  H2O  =  C6H12O6  +  6  O2, 

which  is  the  source  of  all  organic  substances 
and  of  all  the  energy  of  the  organic  cycle  in 
plants  and  animals.  Carbohydrates,  more- 
over, are  the  chief  constituents  of  plants  and 
the  chief  food  of  animals. 

Turning  to  this  synthesis  of  carbohydrate 
in  the  plant,  we  find  much  that  is  important 
in  the  present  study.  The  details  of  the 
chemical  transformation  by  which  water  and 
carbonic  acid  and  solar  energy  are  changed 
to  sugars  and  oxygen  still  remain  unknown, 
in  spite  of  many  careful  investigations.  But, 
at  all  events,  it  is  possible  to  see  that  two 
things  must  somehow  be  done  in  order  to 
accomplish  the  synthesis :  — 

(1)  Carbonic  acid  and  water  must  be  re- 
duced. That  is  to  say,  oxygen  must  be  sepa- 
rated from  both  of  these  compounds  ^o  that 
free  valences  may  exist  to  unite  carbon  and 


228     THE  FITNESS  OF  THE  ENVIRONMENT 

hydrogen  in  one  molecule,  and  so  that,  further, 
the  relative  proportions  of  the  three  elements 
may  become  what  they  are  in  the  simple 
carbohydrates,  C:H:0  =  1:2:1. 

(2)  Somehow  individual  carbon  atoms  must 
be  joined  together  until  there  are  six  in  each 
molecule,  where  formerly  there  was  but  one. 

Theoretically,  it  might  be  possible  by  reduc- 
tion to  form  from  carbon  dioxide  and  water 
without  union  of  carbon  atoms  the  following 
substances:  carbon  monoxide,  CO;  formic 
acid,  H-COOH;  formaldehyde,  H-CHO; 
methyl  alcohol,  CH3OH ;  and  methane,  CH4. 
Of  such  reductions  the  formation  of  formic  acid, 
formaldehyde,  and  carbon  monoxide  has  been 
directly  realized  by  laboratory  experiment.^ 

The  most  familiar  theory  of  the  formation 
of  carbohydrates  in  the  leaf  is  that  of  von 
Baeyer,  which  assumes  a  polymerization  of 
one  of  the  above  substances,  formaldehyde, 
leading  directly  to  the  formation  of  sugar, 
according  to  the  reaction 

6HCHO  =  C6Hi206. 

This  process  also  has  been  carried  out  ex- 
perimentally. Indeed,  as  a  result  of  the 
investigations    of    Butlerow,    O.    Loew,    and 

iSee   Meyer    u.  Jacobson's    "Lehrbuch    der   Organischen 
Chemie,"  Leipzig,  1907,  p.  688,  693-696. 


CHEMISTRY  229 

E.  Fischer,  it  is  known  that  in  distinctly  alka- 
line solutions  formaldehyde  spontaneously  goes 
over  into  a  mixture  of  sugars  which  resemble 
glucose.  Moreover,  such  a  solution  is  un- 
questionably made  up  of  much  the  same 
variety  of  substances  as  a  glucose  solution 
which  has  been  subjected  to  the  action  of 
alkali  in  the  same  concentration. 

As  stated  above,  it  is  evident  that  if  any- 
thing is  to  be  done  chemically  with  a  mix- 
ture of  carbon  dioxide  and  water,  oxygen  must 
be  spht  off  from  both  carbon  and  hydrogen 
so  that  they  may  enter  into  the  same  mole- 
cule. If  this  chemical  change,  which,  to  be 
sure,  is  no  easy  one  in  the  laboratory,  be  ac- 
complished, formaldehyde  among  other  things 
results  ;  and  in  alkaline  solution  formaldehyde 
produces  carbohydrates  and  leads  to  that 
amazing  tangle  of  substances  and  reactions, 
whose  nature  has  been  briefly  indicated  above. 
In  short,  the  one  chemical  process  ivhich  is 
open,  if  any  transformations  whatever  are  to  be 
accomplished  loith  carbonic  acid  and  water, 
leads  directly  and  to  all  appearances  necessarily 
to  the  greatest  complexity  that  has  been  found  in 
any  one  chemical  process  ;  to  a  system  made  up 
of  possibly  two  hundred  substances  or  more, 
most  of  which  possess  very  great  chemical 
activity. 


230     THE  FITNESS  OF  THE  ENVIRONMENT 

It  must  not  be  forgotten  that  the  share  of 
the  organism  in  such  processes  is  also  impor- 
tant. If  possible,  the  smoothness  with  which 
chemical  reactions  are  carried  out  in  the  leaf, 
perhaps  quite  without  any  stop  at  the  formal- 
dehyde stage,  and  the  certainty  with  which 
definite  substances  in  large  amounts  instead 
of  mixtures  in  very  small  amounts  are  pro- 
duced, seem  more  remarkable  than  the  under- 
lying chemical  facts.  Needless  to  say,  one 
great  factor  in  such  processes  is  the  action  of 
enzymes.  Otherwise  we  are  at  a  loss  for  a 
description  of  the  ways  and  means  by  which 
the  organism  operates,  though  the  brilliant 
studies  of  chlorophyll  which  have  recently 
been  carried  out  by  Willstatter  promise  great 
achievements  in  the  future.^ 

The  underlying  chemical  facts,  however, 
remain  ;  carbohydrates  are  among  the  natural 
products  of  carbon  dioxide  and  water;  they 
manifest  in  solution,  especially  in  such  con- 
ditions as  obtain  in  protoplasm  or  the  ocean,^ 
unparalleled  instability  and  variety  of  reac- 
tions ;  and  they  produce  spontaneously  an 
enormous  number  of  very  active  chemical 
substances.     It    is    easy    to    see    that,    given 

^  See  his  many  papers  of  recent  years  in  "Liebig's  Annal- 
len." 

2  Henderson,  Journal  of  Biological  Chemistry,  X,  3,  1911. 


CHEMISTRY  231 

an  enzyme  possessing  the  power  to  select  and 
catalyze  any  one  of  the  reactions,  the  for- 
mation of  any  special  one  of  the  many  possible 
products  in  comparative  purity  is  an  auto- 
matic result. 

Such  processes  are  in  nature  carried  out 
with  a  perfection  which  to  the  chemist  is 
almost  inconceivable,  by  means  of  organic 
structures  of  the  highest  intricacy ;  but  in 
the  last  analysis  they  rest  upon  the  native 
properties  of  the  three  elements. 

The  important  consideration,  I  repeat,  is 
this:  that  reduction,  the  necessary  first  change 
of  carbonic  acid  and  water,  can  lead  directly 
by  a  single  continuous  chemical  transforma- 
tion, of  which  the  exact  control  is  no  whit 
more  remarkable  than  the  accurate  control 
of  the  other  processes  of  chemical  physiology,^ 
to  the  full  intricacy  of  organic  chemistry ;  to 
the  very  most  notable  instance  of  number, 
variety,  and  activity  of  substances,  all  formed 
inevitably,  in  the  nature  of  the  case,  which 
has  yet  come  to  light.  It  is  of  no  consequence 
that  most  of  the  substances  must  be  formed 
in  mere  traces  by  the  spontaneous  synthesis, 
for  in  highest  degree  the  organism  possesses 
the  power,    by  enzymatic  catalysis,  to  select 

^  Consult  the  work  of  Bayliss  on  Enzymes.  London, 
Longmans,  Green  &  Company. 


232     THE  FITNESS  OF  THE  ENVIRONMENT 

any  one  of  a  group  of  simultaneous  reactions 
that  may  serve  its  needs,  and  make  that  one 
predominant.  In  short,  the  fitness  is  recip- 
rocal ;  the  unique  chemical  adaptability  of 
the  process  and  the  unique  chemical  powers  of 
the  living  organism  interlock. 

Such,  in  brief,  are  the  superlative  advan- 
tages which  the  properties  of  the  compounds 
of  the  three  elements  contribute  to  the  organic 
mechanism.  They  include  number  of  sub- 
stances, variety  of  substances,  variety  of 
properties,  variety  of  reactions,  facility  of 
reactions  (instability),  and  the  remarkable 
relationship  between  carbon  dioxide  and  water 
and  the  carbohydrates.  And  they  insure 
that  extreme  variety  of  chemical  relationship 
which  especially  fits  organic  substances,  once 
created,  to  be,  throughout  the  various  forms 
of  life,  the  source  of  still  other  bodies,  and  the 
source  of  energy,  by  means  of  far-reaching 
chemical   changes  rapidly   accomplished. 

G 

HYDROLYSIS 

In  the  course  of  digestion  the  principal 
foodstuffs,  carbohydrates,  fats,  and  proteins, 
undergo  a  series  of  changes  which  are  substan- 
tially the  same  for  all.  Such  processes  are 
known  as  hydrolytic  cleavage,  or  more  loosely 


CHEMISTRY  233 

as  hydrolysis.  Essentially  they  amount  to 
successive  splittings  of  the  large  molecules 
of  the  native  substances,  each  cleavage  being 
accompanied  by  the  addition  of  a  molecule 
of  water,  until  finally  from  starches  and  like 
substances  the  simple  sugars  like  glucose  result; 
from  the  fats,  fatty  acids  and  glycerine ; 
from  the  proteins,  the  so-called  amino  acids. 
The  cleavage  of  fats  closely  resembles  the 
hydrolysis  of  a  simple  ester;  the  cleavage 
of  proteins  and  carbohydrates  a  little  more 
remotely  resembles  the  same  process.  Accord- 
ingly, the  hydrolysis  of  the  simplest  ester, 
methyl  formate,  may  serve  as  an  illustration 
of  the  nature  of  the  reaction:  — 


H-C-O^CHa+H  O 

II 
O 


H  =  H-C-0-H+H-0-CH3 

II 
O 


This  process  is  nothing  less  than  the  typical 
reaction  between  water  and  organic  sub- 
stances. Accordingly,  it  is  not  surprising  that 
such  reactions  are  by  no  means  confined  to 
the  digestion  of  food.  Once  formed,  the  prod- 
ucts of  digestion  are  absorbed,  the  more 
readily  because  of  their  simplicity,  and,  also 
because  of  their  simplicity,  they  carry  into 
the  body  no  trace  of  the  organism  in  which 
they  previously  existed.     But,  if  they  are  to 


234      THE  FITNESS  OF  THE  ENVIRONMENT 

be  built  up  into  the  tissues  of  the  animal, 
they  must  now  be  turned  back  into  such  fats, 
carbohydrates,  and  proteins  as  are  character- 
istic of  his  physical  structure ;  into  glycogen, 
haemoglobin,  fibrinogen,  etc.  Accordingly, 
they  undergo  a  process  which  is  the  exact 
reverse  of  the  digestive  change,  in  the  simple 
case: — 


H-C-0-H  +  H-0-CH3  =  H-C-0-CH3  +  H-0-H 

II  II 

o  o 


But  this  is  by  no  means  the  end  of  the  matter. 
For  example,  glycogen  thus  formed  in  the 
liver  from  the  glucose  of  the  portal  blood  is 
soon  torn  down  to  glucose  again.  More- 
over, there  are  a  host  of  other  special  cases 
of  the  same  hydrolytic  cleavage,  or  the  re- 
verse process,  in  mammalian  physiology.  For 
instance,  the  formation  of  hippuric  acid  from 
benzoic  acid  and  glycocoll,  and  the  formation 
of  urea  itself  from  ammonium  carbonate 
belong  to  this  same  class.  In  fact,  such 
reactions  make  up  a  large  part  of  all  the 
chemical  changes  which  take  place  within 
the  organism. 

It  must  not  be  imagined,  however,  that 
hydrolytic  cleavages  are  infrequent  outside 
the  organism,  or  that  the  types  of  processes 


CHEMISTRY  235 

which  occur  within  the  organism  are  the  only 
ones  of  this  class.  There  is  no  more  common 
and  universally  important  reaction  in  organic 
chemistry,  and  many  compounds  and  classes 
of  compounds  which  have  nothing  to  do  with 
the  organism  undergo  hydrolysis.  Moreover, 
generally  speaking,  all  reactions  of  this  class 
are  very  similar  in  their  principal  character- 
istics, resembling  one  another  both  dynami- 
cally and  statically.  Spontaneously  they  oc- 
cur not  at  all,  or  very  slowly.  Under  the 
influence  of  enzymes,  of  acids,  and  of  alkalies 
acting  catalytically,  that  is  to  say,  facilitating 
the  process  without  in  the  end  taking  part 
in  it,  much  as  oil  facilitates  the  action  of  a 
machine,  they  progress  rather  slowly  and 
very  smoothly.  B^^-products  are  not  formed  ; 
the  reactions  are  simple,  uncomplicated,  and 
reliable.  Hence  they  enable  the  organism  to 
make  all  sorts  of  rearrangements  and  recon- 
structions of  chemical  substances  efficiently 
and  without  loss  of  material. 

The  chief  cause  of  such  traits  in  hydrolysis 
is  the  fact  that  the  energy  transformation 
which  accompanies  the  process  is  almost 
exactly  nil.  For  it  has  been  found  in  general 
that  chemical  reactions  which  liberate  much 
energy  are  violent,  hard  to  regulate,  often 
complicated  by  intricate  side  reactions,  and 


236     THE  FITNESS  OF  THE  ENVIRONMENT 


complete.  In  contrast,  those  which  are  with- 
out energy  change  generally  proceed  smoothly, 
slowly,  and  without  complication  to  a  state  of 
equilibrium  in  which  the  reaction  is  very  in- 
complete.^ Under  the  latter  circumstances 
slight  changes  of  conditions  make  possible 
a  reversal  of  the  delicately  balanced  process; 
the  reaction  can  be  made  to  run  in  either 
direction  at  will. 

The  absence  of  transformation  of  energy 
accompanying  hydrolysis  may  be  illustrated 
by  a  few  typical  cases  chosen  from  the  data 
of  simple   substances. 


Calories 

Per  Cent 

Cane  sugar 

Milk  sugar 

Maltose 

Ethyl  acetate 

+  1.9 
+4.3 
-3.7 

+2.0 

0.2 
0.3 
0.3 
0.3 

Such  measurements  of  heats  of  reaction  fall 
well  within  the  limits  of  error  of  the  method 
of  investigation,  and  there  can  be  no  doubt 
that  in  all  such  cases  the  heat  of  reaction  is 
so  small  that  it  cannot  be  detected  by  the 
ordinary  methods  of  measurement.^ 

^  van't  Hoff,  "Acht  Vortrage  iiber  Physikalische  Chemie." 
Brunswick,  1902,  Lecture  6. 

2  Stohmann,  Zeitschrift  fiir  Physikalische  Chemie,  II,  29, 
1888  (see  also  Ostwald's    "Lehrbuch   der  Allgemeinen  Che- 


CHEMISTRY  237 

Thus  it  is  evident  that  the  process  possesses 
another  advantage.  In  the  course  of  such 
rearrangements  no  energy  is  lost.  This  con- 
chision  is  thoroughly  confirmed  by  the  studies 
of  the  energy  transformations  of  metabolism. 
The  body  may  carry  on  such  processes  as  it 
will,  in  the  greatest  variety  and  complexity, 
rearranging  and  modifying  its  chemical  struc- 
tures to  any  extent,  and  there  will  never  be 
an  appreciable  wastage  of  precious  material 
or  of  equally  precious  energy  in  the  process. 

This  process,  as  we  have  seen,  is  the  char- 
acteristic reaction  between  water  and  the 
organic  compounds.  As  such  it  is  necessarily 
one  of  our  chief  concerns ;  its  maximal  fitness 
as  a  means  of  regulation,  and  otherwise,  there- 
fore assumes  real  importance  in  the  present 
discussion. 

II 

INORGANIC   CHEMISTRY 

With  the  survey  of  organic  chemistry  we 
have   exhausted   the   compounds    of   carbon ; 

mie").  These  data  are  the  most  accurate  now  in  existence 
which  permit  an  estimate  of  the  heat  of  hydrolysis  of  non- 
nitrogenous  compounds.  Numerous  studies  of  protein  deriv- 
atives from  Fischer's  laboratory  prove  that  the  facts  are 
the  same  for  these  substances,  and  direct  measurements 
confirm  the  measurements  of  heats  of  combustion. 


238     THE  FITNESS  OF  THE  ENVIRONMENT 

not  so  those  of  hydrogen  and  oxygen.  In 
almost  equal  frequency  the  latter  elements 
take  part  in  the  reactions  of  inorganic  chem- 
istry, and  help  to  form  its  molecular  struc- 
tures. As  an  illustration  of  their  importance 
in  this  department  of  the  science  I  have 
counted  the  compounds  and  the  classes  of 
compounds  mentioned  in  the  table  of  con- 
tents of  the  second  edition  of  Erdmann's 
* '  Lehrbuch  der  Anorganischen  Chemie. ' '  In  all 
435  substances  are  referred  to ;  of  these  259, 
approximately  60  per  cent,  contain  oxygen ; 
130,  or  30  per  cent,  contain  hydrogen.  There 
seems  to  be  little  doubt  that  this  is  a  fair 
test,  for  the  work  is  compendious,  and  all  im- 
portant substances  and  classes  of  substances 
are  mentioned.  Even  if  the  acids,  and  the 
small  number  of  bodies  which  are  referred  to 
in  connection  with  their  water  of  crystalli- 
zation, be  eliminated  from  the  above  count 
the  great  importance  of  the  two  elements 
remains  clearly  evident. 

Only  about  one  fourth  of  all  the  compounds 
mentioned  contain  neither  hydrogen  nor  oxy- 
gen. A  very  large  proportion  of  these  con- 
sist of  the  chlorides,  bromides,  iodides,  sul- 
phides, fluorides,  and  other  similar  binary 
compounds,  whose  importance  certainly  does 
not    depend    upon    the    variety    of    chemical 


CHEMISTRY  239 

reactions  into  which  they  may  enter,  while 
their  formation  unquestionably  does  depend 
upon  the  intervention  of  both  hydrogen  and 
oxygen.  All  told,  the  chemical  substances 
which  contain  neither  carbon,  nor  hydrogen, 
nor  oxygen  make  up  only  a  few  per  cent  of 
known  bodies. 

It  is  also  clear  that  an  especially  large  pro- 
portion of  the  most  active  inorganic  com- 
pounds contain  either  hydrogen  or  oxygen. 
All  acids  contain  hydrogen ;  most  of  them 
oxygen  as  well.  All  bases  contain  oxygen. 
Moreover,  the  most  important  classes  of  re- 
actions of  inorganic  chemistry  are  probably 
oxidations  and  reductions,  and  the  formation 
of  salts  from  acids  and  bases.  In  such  pro- 
cesses both  oxygen  and  hydrogen  are  con- 
cerned. 

In  addition  to  the  oxides  and  resulting 
bases  and  acids,  a  few  other  important  sub- 
stances which  contain  hydrogen  or  oxygen 
may  be  cited :  ozone  O3,  hydrogen  peroxide 
H2O2,  ammonia  NH3,  hydrazine  N2H4,  hydrox- 
ylamine  NH2OH,  sulphuretted  hydrogen  H2S, 
hydrochloric  acid  HCl,  nitrosyl  chloride  NOCl, 
thionyl  chloride  SOCI2,  phosgene  COCI2,  phos- 
phine  PH3,  phosphorus  oxychloride  POCI3, 
arsine  ASH3.  Such  compounds,  and  many 
other  similar  ones,  are  of  great  importance  on 


240     THE  FITNESS  OF  THE  ENVIRONMENT 

account  of  the  variety  of  chemical  processes 
into  which  they  can  enter.  They  make  up 
the  active  agents  of  inorganic  chemistry,  and 
it  is  safe  to  assume  that  their  activity  depends 
in  great  part  upon  the  properties  of  oxygen 
and  hydrogen. 

The  importance  of  oxygen  and  hydrogen 
in  inorganic  chemistry  possesses  a  double 
significance  in  the  present  inquiry.  In  the 
first  place  it  provides  further  confirmation 
of  the  view  that  the  elements  which  make 
up  water  and  carbon  dioxide  are  unique.  For 
the  data  of  inorganic  chemistry  prove  that 
hydrogen  and  oxygen  are  likely  to  confer 
great  chemical  activity  wherever  they  are, 
and  that  they  are  quite  unrivaled  in  this 
respect.  Secondly,  the  occurrence  of  hydrogen 
and  oxygen  as  primary  factors  of  the  metabolic 
process  and  as  the  chief  constituents  of  the 
environment  and  of  the  living  organism  enables 
the  latter  to  make  use  of  other  elements  at 
need.  Without  hydrogen  and  oxygen,  op- 
portunities for  the  introduction  of  such  other 
elements  into  the  physiological  processes  would 
be  necessarily  much  restricted,  and  in  many 
cases  the  physiological  utility  of  compounds 
containing  the  elements  of  inorganic  chemistry 
is  very  great. 

Chlorophyll,  for    example,    contains    mag- 


CHElVnSTRY  241 

nesium,  and  it  is  thought  that  the  process  of 
reduction  in  the  leaf  may  depend  upon  the 
characteristic  properties  of  this  element;  at 
all  events,  in  organic  chemistry,  magnesium, 
when  employed  in  Grignard's  reaction,  is  one 
of  the  most  effective  agents  to  accomplish 
reductions. 

In  like  manner,  haemoglobin  contains  iron, 
and  the  capacity  of  haemoglobin  to  unite 
with  oxygen,  and  as  oxy haemoglobin  to  carry 
it  from  the  lungs  to  the  tissues  is  unquestion- 
ably due  to  the  chemical  behavior  of  that 
metal.  Other  similar  metallic  elements,  no- 
tably copper  in  the  class  of  compounds  known 
as  haemocyanines,  fulfill  a  similar  function  in 
lower  animals. 

Phosphorus  in  organic  union  is  an  essential 
constituent  of  a  great  variety  of  the  chemical 
structures  of  living  organisms,  —  the  nucleic 
acids,  which  appear  to  be  not  less  important 
than  fats,  carbohydrates,  and  proteids  them- 
selves in  both  animal  and  plant  cells,  contain 
phosphorus  as  an  essential  constituent.  Thus 
phosphorus  follows  close  upon  nitrogen,  after 
carbon,  oxygen,  and  hydrogen,  as  structural 
material  in  biological  chemistry.  This  same 
element  also  occurs  in  many  other  compounds, 
the  simplest  derivative  of  such  bodies  being 
glycerophosphoric  acid, 


242     THE  FITNESS  OF  THE  ENVIRONMENT 

CH2OH 

1 

CHOH 

I 

\  /0-H 

a  compound  of  phosphorus,  hydrogen,  and 
oxygen    with    glycerine. 

Sulphur  is  a  constituent  of  the  proteins, 
and  occurs  in  many  other  important  com- 
pounds. In  the  metabolic  process  of  the 
animal  sulphur  is  converted  from  a  derivative 
of  hydrogen  sulphide,  H2S,  by  oxidation,  into 
sulphuric  acid,  H2SO4,  and  in  the  plant  the 
process  is  reversed. 

Iodine  occurs  in  the  thyroid  and  in  many 
marine  organisms.  The  availability  of  this 
element  depends  upon  its  existence  in  nature 
as  iodides,  that  is  to  say,  upon  its  capacity 
to  unite  with  hydrogen  to  form  hydriodic 
acid,  HI.  Finally,  it  is  the  analogous  com- 
pound of  chlorine  with  hydrogen,  hydro- 
chloric acid,  which  contributes  acidity  to  the 
gastric  juice. 

This  list  might  be  much  further  extended, 
but  I  think  that  the  nature  of  the  case  is  now 
established.     The  conclusion  seems  inevitable 


CHEMISTRY  243 

that  active,  diverse,  and  important  inorganic 
substances  usually  contain  oxygen  or  hydro- 
gen, and  that  it  is  the  union  of  other  elements 
with  these  two  which  renders  them  available 
and  useful  to  the  organism. 

Ill 

THERMOCHEMISTRY 

Every  chemical  change  consists  in  simul- 
taneous rearrangements  of  matter  and  energy. 
The  true  nature  of  the  chemical  process  is  to 
be  sought  neither  in  the  one  nor  in  the  other 
of  these  two  phenomena,  but  in  both  together ; 
and  properly  energy  is  as  much  the  chemist's 
concern  as  matter  itself. 

Thus  far  in  the  present  investigation,  con- 
siderations regarding  energy  have  been  avoided 
except  in  the  case  of  hydrolytic  cleavages,  and 
these  constitute  a  unique  class  of  reactions. 
No  other  large  and  important  class  is  char- 
acterized by  inappreciable  heat  of  reaction, 
for  it  is  as  heat  that  chemical  energy  commonly 
manifests  itself  when  liberated.  It  is  evident, 
however,  in  accordance  with  the  fundamental 
postulates,  that  the  organism  must  have 
energy  to  actuate  as  well  as  matter  to  form 
its  mechanism.  Therefore  the  nature  of  the 
energy  transformations,  which  make  up  one 


244      THE  FITNESS  OF  THE  ENVIRONMENT 

aspect  of  the  chemical  reactions  into  which 
carbon,  hydrogen,  and  oxygen  enter,  must  be 
now  noticed. 

It  has  been  shown  above  that  the  one  pos- 
sible chemical  process  by  means  of  which  any- 
thing can  be  made  out  of  the  primary  con- 
stituents of  the  environment  is  reduction,  — 
the  more  or  less  complete  tearing  off  of  oxygen 
from  carbon  and  hydrogen  atoms  in  the  mole- 
cules of  carbon  dioxide  and  water.  As  a 
function  of  the  extent  of  the  reduction  the 
energy  change  involved  in  the  process  will 
vary.  In  all  cases,  however,  the  process  is 
accompanied  by  large  absorption  of  heat,  as 
the  following  table  of  the  energy  absorbed 
per  gram  of  the  resulting  substance,  when 
reduction  begins  with  water  and  carbonic 
acid,  may  indicate:  — 


H^ 

34.5  Cal 

C 

8.1 

CH, 

13.3 

CH3OH 

5.3 

HCHO 

4.2 

C6H12O6 

3.74 

CO 

2.4 

HCOOH 

1.4 

Such    new    compounds    hold    their    energy 
only  so  long  as  they  persist  unchanged,  and 


CHEMISTRY  245 

upon  oxidation  they  yield  it  all  back  again, 
just  as  water  vapor  on  condensing  yields 
back  the  latent  heat  which  it  has  taken  up 
during  evaporation.  In  this  manner,  every 
gram  of  glucose  or  other  monosaccharide  is 
necessarily  a  temporary  depository  of  solar 
energy  amounting  to  about  3.74  calories, 
taking  up  just  that  amount  of  energy  when 
synthesized  by  chlorophyll,  yielding  it  back 
when  burned  in  the  muscle. 

Compounds  of  carbon  and  hydrogen  are 
especially  well  qualified  to  be  reservoirs  of 
energy  w^hich  may  be  liberated  by  oxidation, 
as  the  following  table  shows:  — 


HEATS  OF  COMBUSTION  OF 

ELEMENTS  PER  GRAM 

Hydrogen 

34.5  Cal. 

Carbon 

8.1 

Sulphur  (to 

SO,) 

2.3 

Sulphur  (to 

SO3) 

3.2 

Nitrogen  (to  NO2) 

0.2 

Phosphorus 

5.9 

Boron 

12.3 

Silicon 

3.3 

Potassium 

1.3 

Calcium 

3.3 

Aluminium 

7.0 

Hydrogen,   it  will  be   seen,   far  exceeds   any 
other  element  in  the  amount  of  heat  that  it 


246    THE  FITNESS  OF  THE  ENVIRONMENT 

yields  upon  oxidation;  carbon  is  surpassed 
by  but  one  other  element,  boron.  Although 
necessarily  a  good  deal  of  this  heat  cannot  be 
stored  in  the  compounds  of  the  two  elements 
which  still  contain  some  oxygen,  yet  enough 
remains  to  make  the  common  constituents 
of  the  organism  greater  reservoirs  of  energy 
than  most  of  the  other  elements  themselves, 
far  greater  than  compounds  of  any  other 
elements.  Thus  the  heat  of  combustion  of 
carbohydrates  ranges  from  about  3.7  calories 
to  about  4.2  calories  per  gram,  that  of  the 
proteins  from  about  5  calories  to  about  6 
calories,  that  of  the  fats  from  about  9.2  calo- 
ries to  about  9.5  calories.  On  account  of  the 
small  quantity  of  oxygen  and  the  large  quan- 
tity of  hydrogen  which  they  contain,  the  fats 
are  a  richer  source  of  energy  than  carbon 
itself,  or  than  any  other  element  except  hydro- 
gen and  boron. 

There  remains  one  other  equally  important 
consideration  to  be  dealt  with:  the  very  great 
energy  change  which  is  involved  in  processes 
of  oxidation  and  reduction  compared  with 
other  chemical  processes.  The  following 
table,  showing  the  amount  of  heat  liberated 
in  the  process  of  formation  of  certain  binary 
compounds  from  their  several  elements,  illus- 
trates the  case: — 


CHEMISTRY 

24 

HEATS  OF 

FORMATION 

H^O 

3.83  Cal. 

CS2 

-0.25  Cal 

CO2 

2.22 

NaCl 

1.67 

HCl 

0.60 

LiCl 

2.20 

HF 

1.97 

NaBr 

0.87 

NH3 

1.23 

NaF 

2.64 

02vyl2 

0.08 

Na^S 

1.14 

CCI4 

0.49 

SiH4 

-0.21 

PI3 

0.26 

SiF4 

2.31 

BCI3 

0.79 

NS 

-0.69 

Ox^^gen,  as  will  be  seen,  far  surpasses  the 
other  chemical  elements  (except  fluorine)  in 
the  amount  of  energy  liberated  in  the  process 
of  its  chemical  union  with  other  substances. 

Accordingly,  it  may  be  concluded  that,  on 
the  whole,  oxidations  are  the  best  chemical 
source  of  energy ;  reductions  the  best  means 
of  storing  energy  by  chemical  processes ; 
and  that  among  oxidations  and  reductions 
those  of  hydrogen  especially,  and  then  those 
of  carbon,  are  associated  with  the  largest 
energy  transformations. 

This  is  the  last  argument  which  I  have  to 
present,  but  it  is  one  of  the  most  potent.  The 
very  chemical  changes,  which  for  so  many 
other  reasons  seem  to  be  best  fitted  to  be- 
come the  processes  of  physiology,  turn  out  to 
be  the  very  ones  which  can  divert  the  greatest 


248    THE  FITNESS  OF  THE  ENVIRONMENT 

flood  of  energy  into  the  stream  of  life;  and 
these  are  the  reactions  automatically  provided 
for  by  the  cosmic  process. 

From  the  materialistic  and  the  energetic 
standpoint  alike,  carbon,  hydrogen,  and  oxy- 
gen, each  by  itself,  and  all  taken  together, 
possess  unique  and  preeminent  chemical  fit- 
ness for  the  organic  mechanism.  They  alone 
are  best  fitted  to  form  it  and  to  set  it  in  motion; 
and  their  stable  compounds,  water  and  car- 
bonic acid,  which  make  up  the  changeless 
environment,  protect  and  renew  it,  forever 
drawing  fresh  energy  from  the  sunshine. 


CHAPTER  VII 
THE  ARGUMENT 

THE  statement  of  evidence  for  the  bio- 
logical fitness  of  the  environment  is  at 
length  completed.  Whatever  favorable  prop- 
erties of  water,  carbonic  acid,  and  the  com- 
pounds of  the  three  elements,  whatever  results 
favorable  to  life,  I  have  succeeded  in  finding, 
have  been  set  forth. 

Now,  therefore,  we  may  return  to  the  exam- 
ination of  this  evidence  in  the  manner  sug- 
gested in  Chapter  11.  We  may  inquire  into 
the  exhaustiveness  of  the  preceding  treatment 
of  important  physical  properties,  seeking  to 
discover  what  things  have  been  overlooked. 
Thus  it  may  be  possible  to  decide  the  weighty 
question  whether  another  group  of  elements 
can  possess  another  group  of  equally  impor- 
tant properties.  Next,  we  may  consider  if 
there  be  other  elements  or  compounds  which 
rival  carbon,  hydrogen  and  oxygen,  water  and 
carbonic  acid,  in  the  qualities  which  make 
these  fit  for  the  organic  mechanism,  taking 
such  properties  as  a  whole.     Unfortunately, 

249 


250     THE  FITNESS  OF  THE  ENVIRONMENT 

in  adopting  this  somewhat  rigid  logical 
method,  tedious  and  perhaps  unnecessary 
repetition  is  involved,  but  the  advantages  of 
care  at  this  stage  of  the  inquiry  seem  to  be 
very  great,  for  it  is  not  easy  to  survey  so 
large  a  field,  and  at  best  certainty  that  impor- 
tant oversights  have  been  avoided  is  obviously 
impossible.  For  example,  peculiarities  like  the 
anomalous  expansion  of  water,  or  the  relation 
of  carbonic  acid  and  water  to  the  carbohy- 
drates are  not  to  be  foreseen.  On  the  other 
hand,  the  more  general  characteristics  of 
matter  are  well  known  and,  for  the  most  part, 
must  reveal  themselves  to  diligent  search. 

I 

ANALYSIS  OF  THE  EVIDENCE 

First  the  natural  phenomena  which  seem  to 
be  concerned  in  fitness  may  be  brought  to- 
gether analytically,  and  their  effect  briefly 
summarized. 

NATURAL    PHENOMENA    WHICH    PROMOTE  FITNESS 
IN  THE  ENVIRONMENT 

I.  The  occurrence  of  great  quantities  of 
water  and  carbon  dioxide  outside 
the  solid  crust  of  an  astronomical 
body. 


THE  ARGUMENT  251 

II.    Properties  of  Water. 

a.  Specific  Heat. 

b.  Freezing  Point. 

c.  Latent  Heat  of  Fusion. 

d.  Latent  Heat  of  Vaporization. 

e.  Vapor  Tension. 

/.     (Thermal  Conductivity.) 
g.    Expansion  before  Freezing. 
h.    (Expansion  in  Freezing.) 
i.     Solvent  Power. 
j.     Dielectric  Constant. 
k.    Ionizing  Power. 
/.     Surface  Tension. 
III.    Properties  of  Carbon  Dioxide. 

a.  Solubility  in  Water. 

b.  Ionization  Constant. 
IV.    Properties  of  the  Ocean. 

a.  Number  and  Variety  of  Constituents. 

b.  Quantity  of  Dissolved  Material. 

c.  Mobility. 

d.  Constancy  of  Temperature. 

e.  Constancy  of  Osmotic  Pressure. 
/.  Constancy  of  Alkalinity. 

g.    Constancy  of  Composition. 
V.    Chemical  Properties  of  Carbon,  Hydro- 
gen, and  Oxygen. 

a.  Number  of  Compounds. 

b.  Variety  of  Compounds. 

c.  Complexity  of  Compounds. 


252     THE  FITNESS  OF  THE  ENVIRONMENT 

d.  Number  of  Reactions. 

e.  Variety  of  Reactions. 

/.     Complexity  of  Reactions. 

g.  The  Evenness  and  Lack  of  Energy 
Change  of  the  Process  of  Hydro- 
lytic  Cleavage. 

h.  The  Chemical  Relationship  of  Car- 
bonic Acid  and  Water  to  the  Sugars. 

i.     Instability  of  the  Sugars. 

j.    Variety  and  Reactions  of  the  Sugars. 

k.  Heats  of  Reaction  in  Organic  Chemis- 
try. 

Z.  The  Number  and  Variety  of  Com- 
pounds and  Reactions  of  Oxygen 
with  Other  Elements. 

m.  The  Number  and  Variety  of  Com- 
pounds and  Reactions  of  Hydro- 
gen with  Other  Elements. 

All  the  properties  or  other  phenomena 
noted  in  the  above  table  (except  II  /,  and  II  h) 
are  in  character  or  in  magnitude  either  unique 
or  nearly  so,  and  are  in  their  effect  favorable 
to  the  organism  as  defined  in  the  fundamental 
postulates.  Indeed,  they  constitute  or  bring 
about  an  extraordinary  set  of  conditions 
favorable  to  life,  —  ubiquity,  abundance,  va- 
riety, stability,  mobility,  constancy  of  composi- 
tion, and  in  variance  of  physico-chemical  con- 


THE  ARGUMENT  253 

ditions  in  the  environment ;  number,  variety, 
complexity,  adaptability,  availability,  activity, 
and  richness  in  energy  of  the  substances  which 
take  part  in  the  metabolic  processes  and  in 
the  chemical  and  physical  formation  of  the 
organism ;  constancy  of  physico-chemical  con- 
ditions, such  as  temperature,  alkalinity,  col- 
loidal disperseness,  etc.,  within  the  organism; 
the  efficiency  of  many  physiological  processes ; 
the  availability  of  electrical  forces,  etc. 

In  short,  by  many  independent  and  united 
actions  the  above  catalogued  natural  char- 
acteristics of  the  environment  promote  and 
favor  complexity,  regulation,  and  metabo- 
lism, the  three  fundamental  characteristics 
of  life  upon  which  all  our  discussion  has 
been  based. 

II 

THE  EXHAUSTIVENESS  OF  THE  TREATMENT 

One  manner  of  judging  the  completeness 
with  which  different  types  of  phenomena  and 
properties,  different  elements  and  compounds, 
have  been  considered  in  the  descriptive  chap- 
ters preceding  is  to  glance  at  the  several 
departments  of  physical  science,  —  chemistry, 
mechanics,  heat,  sound,  light,  magnetism,  elec- 
tricity, and  physical  chemistry. 


254    THE   FITNESS  OF  THE  ENVIRONIMENT 

In  setting  out  to  consider  physical  and 
chemical  properties  we  may  perhaps  begin 
with  chemical  phenomena  in  the  narrowest 
sense.  Such  phenomena  depend,  according 
to  the  atomic  theory,  upon  rearrangements 
of  atoms  within  molecules.  They  result  in 
the  conversion  of  individual  substances  into 
one  another,  and  they  are  accompanied  by 
rearrangements  of  energy. 

In  the  first  place,  it  is  to  be  noted  that 
enormous  quantities  of  carbon,  hydrogen, 
and  oxygen,  as  water  and  carbonic  acid,  are, 
during  a  very  long  period  of  time,  apparently 
inevitable  constituents  of  the  atmosphere  of 
an  astronomical  body  of  sufficient  size,  after 
cooling  has  led  to  the  formation  of  a  crust. 
Further,  it  has  been  shown  that  in  number, 
variety,  complexity  of  forms  and  changes,  and 
in  the  magnitude  of  the  accompanying  trans- 
formations of  energy  the  known  substances 
made  up  of  carbon  and  hydrogen,  and  those 
made  up  of  carbon,  hydrogen,  and  oxygen  far 
surpass  the  compounds  of  any  other  elements. 
Likewise  the  known  compounds  of  oxygen  and 
hydrogen  with  other  elements  are  the  most 
numerous  and  important  among  inorganic 
substances.  Two  peculiarities  of  the  carbon 
compounds,  the  formation  and  properties  of 
the  carbohydrates,  and  the  nature  of  the  pro- 


THE  ARGUMENT  ^55 

cess  known  as  hydrolytic  cleavage,  add  to  this 
list  of  chemical  characteristics  which  make 
for  fitness. 

These  facts  appear  to  indicate  that  in  gen- 
eral chemical  behavior,  in  certain  special 
characteristics  as  well,  and  in  the  magnitude 
of  the  quantity  of  energy  rendered  available 
by  their  chemical  changes,  the  elements  car- 
bon, hydrogen,  and  oxygen  are  uniquely  and 
most  highly  fitted  to  be  the  stuff  of  which  life 
is  formed  and  of  the  environment  in  which  it 
exists. 

Mechanics  has  taken  a  place  subordinate 
to  chemistry  in  the  present  work.  Neverthe- 
less, it  has  been  noted  that  the  unique  proper- 
ties of  water  are  the  cause  of  the  admirable 
mobility  of  that  substance  and  of  the  whole 
environment,  and  therefore  of  the  dynamical 
processes  of  geology,  meteorology,  etc.,  in- 
cluding soil  formation ;  that  it  is  surface  ten- 
sion which  holds  water  in  the  soil ;  that  the 
efficacy  of  water  as  a  means  of  dissolving  the 
greatest  variety  of  substances  in  the  greatest 
amounts,  makes  possible  high  osmotic  pres- 
sures, as  well  as  mobility  of  all  the  elements ; 
and  there  are  a  host  of  other  considerations 
which  have  been  discussed  above.  In  all 
such  cases  the  properties  of  water  have  been 
found  to  be  favorable  influences  for  the  wel- 


256    THE  FITNESS  OF  THE  ENVIRONMENT 

fare  of  the  organism.  Considering  the  com- 
parative unimportance  of  mechanics  in  rela- 
tion to  the  fundamental  postulates,  it  seems 
clear  that  this  department  has  not  been  over- 
looked. 

Thermal  processes  and  thermal  effects  are 
perhaps  more  conspicuous  in  the  table.  The 
thermochemical  characteristics  of  organic  com- 
pounds and  the  thermal  properties  of  water 
are  all  very  favorable  to  life.  Stores  of  heat 
for  the  organism,  constancy  of  temperature 
of  both  organism  and  environment,  the  per- 
manence of  bodies  of  water,  and  a  multitude 
of  other  most  important  results  flow  from  these 
properties  and  bear  witness  to  their  unique 
fitness. 

Sound,  light,  and  magnetism  have  not  been 
considered,  for  they  appear  to  bear  only  a 
secondary  relation  to  the  fundamental  postu- 
lates. 

In  electricity  no  phenomena  are  more  im- 
portant than  those  of  ionization  in  solution. 
To  bring  about  ionization  and  thus  make 
possible  electrochemical  processes,  water  is 
the  very  best  medium,  and  the  possibility  of 
such  processes  is  probably  necessary  to  the 
organic  mechanism. 

In  addition  to  the  topics  of  physical  chem- 
istry   already    referred    to    under    chemistry 


THE  ARGUMENT  257 

and  the  several  departments  of  physics,  the 
colloids  and  the  ions  of  hydrogen  and  hydroxy] 
remain  to  be  mentioned.  It  has  been  shown 
that  the  properties  of  water  are  exceptionally 
favorable  to  the  existence  and  stability  of 
colloidal  systems ;  also  that  the  properties  of 
carbonic  acid  result  in  automatic  regulation 
of  the  concentration  of  hydrogen  and  hydroxyl 
ions  in  the  ocean  and  in  the  organism. 

So  far,  then,  as  it  is  possible  to  judge  by 
telling  over  the  departments  of  physical 
science,  our  examination  of  physical  and  chem- 
ical properties  has  not  been  incomplete. 

This  conclusion  may  be  further  tested  with 
the  help  of  the  ideas  which  underlie  Willard 
Gibbs's  "  Phase  Rule."  ^  According  to  this  rule, 
the  condition  of  equilibrium  in  any  material 
system  depends  upon  the  number  of  its  com- 
ponents, the  number  of  its  phases,  temperature, 
pressure,  and,  in  general,  the  concentrations 
of  all  the  components.  Without  entering 
upon  an  explanation  of  the  exact  mathemat- 
ical notions  which  determine  the  meaning 
of  the  terms  *'  component "  and  **  phase  "  it 
will  here  suffice  to  say  that  in  general  the 
number  of  components  increases  as  the  num- 
ber of  separate  chemical  individuals  increases, 

^  See,  for  instance,  Findlay,  "The  Phase  Rule  and  its 
Applications."     London,  1911,  3d  ed. 


258     THE  FITNESS  OF  THE  ENVIRONMENT 

and  that  a  phase  is  any  soKd,  hquid,  or  gas- 
eous part  of  the  whole  system  which  possesses 
homogeneity  of  composition.  For  instance, 
if  a  system  is  made  up  of  sand,  salt  solution, 
ice,  and  aqueous  vapor,  each  of  these  separate 
parts,  in  that  it  is  homogeneous,  is  a  phase. 

Now  the  properties  of  water  have  the  result 
that  more  readily  than  other  substances  it 
exists  simultaneously  and  in  large  quanti- 
ties in  the  three  phases  of  solid,  liquid,  and 
gas  as  ice,  water,  and  aqueous  vapor.  This 
depends  upon  the  high  latent  heats  of  fusion 
and  vaporization,  the  high  freezing  point  of 
water,  and  its  vapor  tension.  Water  en- 
hances the  complexity  of  the  environment, 
and  is  one  principal  factor  in  the  mobility  of 
the  environment  as  a  whole.  Further,  it 
makes  for  stability ;  other  things  being  equal, 
the  greater  the  number  of  phases,  the  less  the 
tendency  to  change.  Among  phases  the  dis- 
perse colloidal  type  is  unique  and  of  very 
great  importance  —  almost  the  sole  basis, 
indeed,  of  great  physical  complexity  —  and, 
as  above  shown,  the  peculiar  properties  of 
water  highly  favor  the  colloidal  condition. 

The  solvent  power  of  water  much  increases 
the  number  of  components  which  may  enter 
into  a  system  of  which  it  is  a  part ;  hence  the 
large   number   of   components   of   sea   water. 


THE  ARGUMENT  259 

blood  plasma,  etc.  The  variety  of  compounds, 
both  organic  and  inorganic,  which  contain 
carbon,  hydrogen,  or  oxygen  also  causes  enor- 
mous increase  in  the  number  of  components 
of  biological  systems  like  protoplasm. 

The  effects  of  the  properties  of  water  above 
enumerated  to  regulate  temperature  are  almost 
too  numerous  to  mention.  The  specific  heat 
of  water,  its  latent  heats  of  fusion  and  vapori- 
zation, and  the  high  freezing  point  all  con- 
tribute to  the  restriction  of  temperature  range 
within  the  organism,  in  the  waters,  and  over 
the  whole  surface  of  the  earth.  The  vapor 
pressure  of  water  has  been  shown  to  possess 
great  and  exceptional  variability  with  change 
of  temperature.  This  is  the  m-ost  impor- 
tant property  of  water  meteorologically,  and 
is  the  necessary  condition  for  its  ample  cir- 
culation. The  ratio  between  the  gas  pressure 
of  carbonic  acid  and  its  concentration  in 
water  (absorption  coefficient)  has  been  shown 
to  be  the  great  factor  in  establishing  the  mo- 
bility of  that  substance.  The  total  atmos- 
pheric pressure  has  not  entered  into  our  dis- 
cussion, for  it  seems  to  have  no  important 
special  relation  to  the  properties  of  the  three 
elements. 

In  short,  the  properties  of  water  and  of  the 
carbon  compounds  provide  for  number,  va- 


260     THE  FITNESS  OF  THE  ENVIRONMENT 

riety,  and  complexity  of  phases  and  compo- 
nents, and  for  constancy  of  temperature,  while 
equally  important  and  unique  relationships 
between  the  properties  of  water  and  carbonic 
acid  and  their  vapor  or  gas  pressures  exist, 
and  exert  much  influence  upon  the  meteoro- 
logical cycle. 

Thus,  judged  by  the  phase  rule,  the  actual 
characteristics  of  the  environment  may  be 
shown  to  contribute  the  factors  which  make  for 
complexity  and  regulation  of  material  sys- 
tems. Now  there  can  be  no  doubt  that,  when 
feasible,  the  ideal  method  —  from  the  physico- 
chemical  point  of  view  —  to  describe  a  ma- 
terial system  is  in  the  terms  of  the  phase 
rule.^     Hence  the  characteristics  which  that 

^  "Ten  years  after  the  law  of  mass  action  was  propounded 
by  Guldberg  and  Waage,  Willard  Gibbs,  Professor  of  Physics 
in  Yale  University,  showed  how,  in  a  perfectly  general  manner, 
free  from  all  hypothetical  assumptions  as  to  the  molecular 
condition  of  the  participating  substances,  all  cases  of  equi- 
librium could  be  surveyed  and  grouped  into  classes,  and  how 
similarities  in  the  behavior  of  apparently  different  kinds  of 
systems,  and  differences  in  apparently  similar  systems,  could 
be  explained. 

"  As  the  basis  of  his  theory  of  equilibria,  Gibbs  adopted  the 
laws  of  thermodynamics,  a  method  of  treatment  which  had 
first  been  employed  by  Horstmann.  In  deducing  the  law  of 
equilibrium,  Gibbs  regarded  a  system  as  possessing  only  three 
independently  variable  factors  —  temperature,  pressure,  and 
the  concentration  of  the  components  of  the  system  —  and  he 
enunciated  the  general  theorem  now  usually  known  as  the 


THE  ARGUMENT  261 

rule  contemplates  are  in  certain  respects  the 
most  important  of  characteristics.  Accord- 
ingly the  above  test  is  a  valuable  indication 
of  the  adequacy  of  the  preceding  analysis  of 
physical  and  chemical  properties. 

In  order  if  possible  to  discover  the  nature 
of  such  properties  of  matter  as  may  have  been 
omitted  in  our  study  of  fitness,  I  have  ex- 
amined the  index  of  Landolt  and  Bornstein's 
"  Physikalisch-chemischen  Tabellen,"  a  very 
extensive  and  comprehensive  work.  In  addi- 
tion to  information  regarding  the  arbitrary 
units  of  physical  science,  I  find  mention  of  the 
following  properties  which  have  not  been 
considered  in  the  present  discussion:  — 

The  Mechanical  Equivalent  of  Heat. 

The  Dimensions  of  the  Angles  of  Crystals. 

The  Refraction  of  Light. 

C  ompressibility . 

The  Dimensions  of  the  Molecules  of  Gases. 

Elasticity. 

The  Electromagnetic   Rotation  of   the  Plane 

of  Polarization  of  Light. 
Color. 

Phase  Rule,  by  which  he  defined  the  conditions  of  equilibrium 
as  a  relationship  between  the  number  of  what  are  called  the 
phases  and  the  components  of  the  system."  —  Findlay, 
"The  Phase  Rule  and  its  Applications."  London,  1911,  3d 
ed.,  p.  8. 


262     THE  FITNESS  OF  THE  ENVIRONMENT 

Viscosity. 

Torsion. 

The  Velocity  of  the  Molecules  of  Gases. 

Hardness. 

Magnetism. 

The  Velocity  of  Light. 

Optical  Activity. 

Friction. 

The  Velocity  of  Sound. 

The  Wave  Length  of  Light. 

The  Length  of  the  Path  of  a  Gaseous  Particle. 

To  these  may  be  added  the  phenomena  of 
radioactivity,  etc. 

It  is  clear  that  in  the  present  state  of 
knowledge  the  consideration  of  most  of  these 
properties  is  uncalled  for.  However,  it  may 
perhaps  be  noted  in  passing  that  the  com- 
pressibility of  water  is  remarkably  small,  that 
of  protoplasm  even  less.^  Hence  even  great 
changes  in  pressure  do  not  readily  damage  the 
organism,  and,  indeed,  a  frog's  muscle  appears 
to  function  normally  after  undergoing  a 
pressure  of  500  atmospheres.^  Further,  it  is 
of  decided  consequence  for  many  reasons 
that  the  optical  properties  of  water  are  such 

1  Henderson  and  Brink,  American  Journal  of  Physiology, 
XXI,  248,  1908. 

2  Henderson,  Leland,  and  Means,  American  Journal  of 
Physiology,  XXII,  48,  1908. 


THE  ARGUMENT  263 

that  light  readily  penetrates  it  to  considerable 
depths.  As  for  color,  landscape  and  modern 
chemical  industry  alike  testify  to  the  availa- 
bility of  carbon  compounds  as  its  source. 

A  final  test  of  thoroughness  may  be  based 
upon  a  consideration  of  other  compounds 
and  elements.  Accepting  the  decision  that 
no  other  properties  can  be  so  important  to 
an  active,  complex,  and  regulated  mechan- 
ism as  those  possessed  nearly  or  quite  as 
maxima  by  water,  carbonic  acid,  and  the 
compounds  of  the  three  elements,  what  are 
the  possibilities  of  obtaining  the  same  char- 
acteristics from  other  substances  ? 

So  far  as  chemical  substances  are  now 
known,  the  only  compound  which  can  be  even 
considered  on  this  score  as  a  substitute  for 
water  in  the  environment  is  ammonia,  and 
in  many  respects,  no  doubt,  ammonia  might 
serve  as  well.^     However,  chemical  processes 

^  A  full  discussion  of  the  properties  of  ammonia  which  qual- 
ify it  as  a  substitute  for  water  in  the  role  of  solvent  and  other- 
wise will  be  found  in  the  article  by  E.  C.  Franklin,  "The 
Ammonia  System  of  Acids,  Bases,  and  Salts,"  American  Chem- 
ical Journal,  Vol.  47,  p.  285,  1912.  In  this  paper  the  re- 
sults of  a  long  series  of  investigations  are  brought  together. 
Especially  important  for  the  present  purpose  are  the  intro- 
ductory remarks.  "The  many  striking  analogies  between 
liquid  ammonia  and  water  as  electrolytic  solvents  have  been 
emphasized  by  the  writer  and  his  co-workers  in  papers  which 
have  appeared  from  time  to  time  during  the  past  decade.     In 


264     THE  FITNESS  OF  THE  ENVIRONMENT 

being  what  they  are,  it  is  impossible  to  im- 
agine the  presence  of  vast  amounts  of  am- 
monia in  an  atmosphere,  while  the  loss  of 
the  greater  part  of  the  energy  which  can  be 
stored  by  tearing  apart  hydrogen  and  oxygen 
would  be  a  very  serious  difficulty;  but  the 
loss  of  substantially  all  the  incomparable 
chemical  activity  of  oxygen  is  to  all  appear- 
ances an  insurmountable  obstacle  to  the  sub- 
stitution of  ammonia  for  water  in  biological 
processes. 

From  time  to  time,  loose  discussion  has 
arisen  among  chemists  as  to  the  possibility 
of  substituting  another  element  for  carbon  in 
the  organic  cycle.  Such  speculations  have 
never  been  serious,   but  they  have  at  least 

all  those  properties  which  give  to  water  its  unique  position 
among  solvents,  such  as  its  abnormally  high  boiling  point, 
its  high  specific  heat,  its  high  heat  of  volatilization,  its  high 
critical  temperature  and  pressure,  its  high  association  con- 
stant,-its  high  dielectric  constant,  and  its  low  boUing-point 
elevation  constant,  its  power  as  an  electrolytic  solvent,  and 
the  facility  with  which  it  forms  compounds  with  salts,  liquid 
ammonia  shows  a  remarkable  similarity  to  water." 

"While  the  boiling  point  of  liquid  ammonia  is  33.46°  below 
zero,  it  still  appears  abnormally  high  when  compared  with 
the  boiling  temperatures  of  phosphine,  arsine,  stibine,  me- 
thane, ethylene,  hydrogen  sulphide,  hydrochloric  acid,  etc. 
The  specific  heat  of  liquid  ammonia  and  the  heat  of  fusion 
of  the  solid  are  greater  than  the  corresponding  constants 
for  water  or  any  other  known  substance,  while  its  heat  of 
volatilization,  with  the  one  exception  of  water,  is  the  highest 


THE  ARGUMENT  265 

demonstrated  that  very  few  elements,  prob- 
ably only  silicon,  and  perhaps  boron,  can 
even  be  imagined  in  such  a  role.  It  has, 
moreover,  just  been  shown  that  there  are 
many  facts  leading  to  the  conclusion  that 
only  carbon  among  elements,  and  carbon  itself 
only  in  conjunction  with  hydrogen,  has  the 
power  to  form  the  skeletons  of  compounds 
numerous,  complex,  and  varied  like  those  of 
organic  chemistry.  But,  apart  from  this 
conclusion,  it  is  certain  that  silicon  and  boron 
could  not  be  mobilized  like  carbon.     Quartz, 

of  any  known  liquid.  The  critical  temperature  of  ammonia 
is  abnormally  high,  and  its  critical  pressure  —  the  more  char- 
acteristic constant  —  is  higher  than  that  of  any  other  liquid 
excepting  water.  Ammonia  is  an  associated  liquid,  and  its 
dielectric  constant,  though  much  below  that  of  water,  is  still 
high  when  compared  with  that  of  non-electrolytic  solvents. 
Its  boiling-point  elevation  constant  is  the  lowest  of  any 
known  liquid,  namely  3.4,  as  compared  with  5.2  for  water. 
In  its  tendency  to  unite  with  salts  and  other  compounds,  it 
probably  exceeds  water,  since  salts  with  ammonia  of  crystal- 
lization are  perhaps  even  more  numerousl}^  recorded  in  the 
literature  than  are  salts  with  water  of  crystallization.  As  a 
solvent  for  salts  it  is  generally  much  inferior  to  water,  though 
some  salts,  for  example  the  iodides  and  bromides  of  mercury, 
lead,  and  silver,  dissolve  very  much  more  abundantly  in 
ammonia  than  they  do  in  water,  and  it  far  surpasses  the  latter 
solvent  in  its  ability  to  dissolve  the  compounds  of  carbon. 
Finally  it  exhibits  conspicuous  power  as  an  ionizing  solvent, 
the  more  dilute  ammonia  solutions  at  33.5°  being  very  much 
better  conductors  of  electricity  than  aqueous  solutions  of  the 
same  concentration  at  18°." 


266     THE  FITNESS  OF  THE  ENVIRONMENT 

the  oxide  of  silicon,  is  the  most  inert  and 
immobile  of  rocks ;  the  oxide  of  boron  is  only 
less  available  as  a  movable  constituent  of  the 
environment;  and  there  is  no  other  stable 
compound  of  either  element  which  can  be 
compared  with  carbonic  acid  for  its  mobility. 
It  must  be  remembered  that  this  property 
is  the  result  of  two  independent  characteris- 
tics of  the  latter  substance,  its  gaseous  na- 
ture, and  the  precise  degree  of  its  solubility 
in  water.  Finally,  the  regulation  of  the 
reaction  of  aqueous  solutions  by  means  of 
carbonic  acid  has  to  be  taken  into  account. 

Hence  it  may  be  concluded  that  hydrogen, 
oxygen,  and  carbon,  water  and  carbonic 
acid,  are  not  to  be  rivaled  in  their  own  qual- 
ities, even  as  these  cannot  be  balanced  by 
others  which  they  do  not  possess. 

On  the  whole,  then,  we  may  believe  that  the 
physico-chemical  characteristics  of  material 
systems  and  material  processes  have  been  com- 
prehensively examined  in  the  course  of  the 
present  study.  Accordingly,  we  may  finally 
conclude  that  the  fitness  of  water,  carbonic 
acid,  and  the  three  elements  make  up  a  unique 
ensemble  of  fitness  for  the  organic  mechanism. 
The  search,  however  incomplete,  has  certainly 
not  overlooked  properties  so  important  and 
so  numerous,  or  compounds  and  elements  so 


THE  ARGUMENT  267 

unique,  as  those  which  have  been  considered 
and  set  forth. 

With  the  assurance  that,  in  such  measure 
as  the  present  state  of  science  permits,  our 
study  has  been  indeed  exhaustive,  a  final 
argument  arises.  So  far  as  we  can  see,  all  the 
properties  of  water,  carbonic  acid,  and  the 
three  elements  are  fit,  according  to  our  defi- 
nition of  fitness.  There  is  nothing  about  these 
substances  that  is  really  and  seriously  inferior 
to  the  same  thing  in  any  other  substance; 
and  in  all  the  subjects  which  we  have  reviewed 
not  a  single  disability  of  the  primary  constit- 
uents of  the  environment  has  come  to  light. 

Ill 

SUMMARY 

For  the  convenience  of  my  readers  the  argu- 
ment which  has  been  developed  in  the  course 
of  the  preceding  pages  is  here  re-stated  in 
outline. 

I.  Fitness  is  a  mutual  or  reciprocal 
relationship  between  the  organ- 
ism and  the  environment. 
II.  Life  is  a  mechanism  (from  the 
point  of  view  of  physical  sci- 
ence) .    Accordingly  it  must  be  — 


268     THE  FITNESS  OF  THE  ENVIRONMENT 

a.  Complex  (physically,  chemically, 
physiologically) . 

6.  Durable,  hence  well  regulated 
physico-chemically.  This  con- 
clusion applies  to  — 

1.  The  Organism. 

2.  The  Environment. 

c.  Endowed  with  a  metabolism. 
Hence  there  must  be  ex- 
change with  the  environment 
of  — 

1.  Matter. 

2.  Energy. 

III.  The  primary  constituents  of  the  natural 

environment  are  — 
a.   Water. 
h.    Carbonic  acid. 

IV.  In   places    where    life    is    possible    the 

primary  constituents  of  the 
environment  are  necessarily 
and  automatically  formed  in 
vast  amounts  by  the  cosmic 
process. 
V.  Water,  carbonic  acid,  and  their  con- 
stituent elements  manifest 
great  fitness  for  their  biologi- 
cal role. 
a.  Water  possesses  a  great  number  of 
unique  or  very  unusual  prop- 


THE  ARGUMENT  269 

erties,  e.g.  thermal  proper- 
ties, solvent  power,  dielectric 
constant,  surface  tension, 
which  together  result  in  max- 
imal fitness  in  certain  respects, 
e.g.  mobility,  ubiquity,  con- 
stancy of  temperature  and 
richness  of  the  environment, 
richness  of  the  organism  in 
chemical  constituents,  variety 
of  chemical  processes,  electri- 
cal phenomena,  colloidal  phe- 
nomena. 

6.  Carbon  dioxide  possesses  very  un- 
usual properties,  e.g.  mag- 
nitude of  absorption  coeffi- 
cient, strength  as  acid,  which 
together  result  in  maximal  fit- 
ness in  certain  respects,  e.g. 
mobility,  ubiquity,  richness  of 
the  environment  and  organ- 
ism in  other  elements  and 
compounds,  constancy  of  re- 
action, etc. 

c.  Chemical  compounds  containing 
carbon,  hydrogen,  and  oxygen 
possess  unique  properties,  e.g. 
number,  variety,  complexity, 
activity,   variety   of   chemical 


270     THE   FITNESS  OF  THE  ENVIRONMENT 

relations  and  reactions,  heats 
of  reaction,  instability,  etc., 
which  together  result  in  maxi- 
mal fitness  in  certain  respects, 
e.g.  as  sources  of  matter  and 
energy  for  the  processes  of 
metabolism,  as  sources  of  com- 
plex structures,  as  the  means 
of  establishing  complex  func- 
tions, etc. 
VI.  Oceans  are  formed  automatically  in 
the  cosmic  process. 
VII.  The  ocean  possesses  unique  properties, 
e.g.  mobility,  richness  in  dis- 
solved substances,  durability, 
and  stability  of  physico-chem- 
ical conditions,  depending 
chiefly  upon  the  properties  of 
water  and  carbonic  acid,  which 
together  result  in  maximal  fit- 
ness in  certain  respects,  e.g. 
as  milieu,  and  as  source  of 
matter  for  the  processes  of 
metabolism,  to  moderate  and 
equalize  temperature,  etc. 
VIII.  The  physical  and  chemical  properties 
which  have  been  taken  into 
consideration  include  nearly 
all  those  which  are  known  to 


THE  ARGUMENT  271 

be  of  biological  importance 
or  which  appear  to  be  related 
to  complexity,  regulation,  and 
metabolism. 

IX.  There  are  no  other  compounds  which 
share  more  than  a  small  part 
of  the  qualities  of  fitness  of 
water  and  carbonic  acid ;  no 
other  elements  which  share 
those  of  carbon,  hydrogen,  and 
oxygen. 
X.  None  of  the  characteristics  of  these 
substances  is  known  to  be 
unfit,  or  seriously  inferior  to 
the  same  characteristic  in  any 
other  substance. 

XI.    Therefore  the  fitness   of  the  environ- 
ment is  both  real  and  unique. 

In  drawing  this  final  conclusion  I  mean  to 
assert   the   following   propositions :  — 

I.  The  fitness  of  the  environment  is  one 
part  of  a  reciprocal  relationship  of  which  the 
fitness  of  the  organism  is  the  other.  This 
relationship  is  completely  and  perfectly  recip- 
rocal ;  ^  the  one  fitness  is  not  less  important 

^  This  is  not  to  be  understood  as  an  assertion  that  the  rela- 
tionship is  symmetrical.  The  fact  is  that  each  organism  fits 
its  particular  environment,  while  the  environment  in  its  most 
general  and  universal  characteristics  fits  the  most  general  and 
universal  characteristics  of  the  organic  mechanism. 


272     THE  FITNESS  OF  THE  ENVIRONMENT 

than  the  other,  nor  less  invariably  a  constitu- 
ent of  a  particular  case  of  biological  fitness ; 
it  is  not  less  frequently  evident  in  the  char- 
acteristics of  water,  carbonic  acid,  and  the 
compounds  of  carbon,  hydrogen,  and  oxygen 
than  is  fitness  from  adaptation  in  the  char- 
acteristics of  the  organism. 

II.  The  fitness  of  the  environment  results 
from  characteristics  which  constitute  a  series 
of  maxima  —  unique  or  nearly  unique  prop- 
erties of  water,  carbonic  acid,  the  compounds 
of  carbon,  hydrogen,  and  oxygen  and  the 
ocean  —  so  numerous,  so  varied,  so  nearly 
complete  among  all  things  which  are  concerned 
in  the  problem  that  together  they  form  cer- 
tainly the  greatest  possible  fitness.  No  other 
environment  consisting  of  primary  constitu- 
ents made  up  of  other  known  elements,  or 
lacking  water  and  carbonic  acid,  could  possess 
a  like  number  of  fit  characteristics  or  such 
highly  fit  characteristics,  or  in  any  manner 
such  great  fitness  to  promote  complexity, 
durability,  and  active  metabolism  in  the  organic 
mechanism  which  we  call  life. 

It  must  not  be  forgotten  that  the  possibility 
of  such  conclusions  depends  upon  the  universal 
character  of  physics  and  chemistry.  Out  of 
the  properties  of  universal  matter  and  the 
characteristics  of  universal  energy  has  arisen 


THE  ARGUMENT  273 

mechanism,  as  the  expression  of  physico- 
chemical  activity  and  the  instrument  of  physico- 
chemical  performance.  Given  matter,  energy, 
and  the  resulting  necessity  that  life  shall  be 
a  mechanism,  the  conclusion  follows  that  the 
atmosphere  of  solid  bodies  does  actually  pro- 
vide the  best  of  all  possible  environments  for 
life. 


CHAPTER  VIII 
LIFE  AND  THE  COSMOS 

I 

THE  SIGNIFICANCE  OF  FITNESS 

A  HALF  century  has  passed  since  Darwin 
wrote  "The  Origin  of  Species,"  and  once 
again,  but  with  a  new  aspect,  the  relation 
between  Hfe  and  the  environment  presents 
itself  as  an  unexplained  phenomenon.  The 
problem  is  now  far  different  from  what  it  was 
before,  for  adaptation  has  won  a  secure  posi- 
tion among  the  greatest  of  natural  processes, 
a  position  from  which  we  may  suppose  it  is 
certainly  never  to  be  dislodged ;  and  natural 
selection  is  its  instrument,  even  if,  as  many 
think,  not  the  only  one.^     Yet  natural  selec- 

^  Natural  selection  remains  still  a  vera  causa  in  the  origin 
of  species;  but  the  function  ascribed  to  it  is  practically 
reversed.  It  exchanges  its  former  supremacy  as  the  supposed 
sole  determinant  among  practically  indefinite  possibilities 
of  structure  and  function,  for  the  more  modest  position  of 
simply  accelerating,  retarding,  or  terminating  the  process  of 
otherwise  determined  change.  It  furnishes  the  brake  rather 
than  the  steam  or  the  rails  for  the  journey  of  life ;  or  in  better 

274 


LIFE  AND  THE   COSMOS  275 

tion  does  but  mold  the  organism ;  the  environ- 
ment it  changes  only  secondarily,  without 
truly  altering  the  primary  quality  of  environ- 
mental fitness.  This  latter  component  of  fit- 
ness, antecedent  to  adaptations,  a  natural 
result  of  the  properties  of  matter  and  the 
characteristics  of  energy  in  the  course  of 
cosmic  evolution,  is  as  yet  nowise  accounted 
for.  It  exists,  however,  and  must  not  be 
dismissed  as  gross  contingency.  The  mind 
balks  at  such  a  view.  Coincidences  so  nu- 
merous and  so  remarkable  as  those  which 
we  have  met  in  examining  the  properties  of 
matter  as  they  are  related  to  life,  must  be  the 

metaphor,  instead  of  guiding  the  ramifications  of  the  tree 
of  life,  it  would,  in  Mivart's  excellent  phrase,  do  little  more 
than  apply  the  pruning  knife  to  them.  In  other  words,  its 
functions  are  mainly  those  of  the  third  Fate,  not  the  first,  of 
Siva,  not  of  Brahma.  —  Patrick  Geddes  and  J.  Arthur 
Thomson,  "Evolution."  New  York,  Home  University  Li- 
brary, 1911,  p.  248. 

"But  as  my  conclusions  have  lately  been  much  misrep- 
resented, and  it  has  been  stated  that  I  attribute  the  modifica- 
tion of  species  exclusively  to  natural  selection,  I  may  be 
permitted  to  remark  that  in  the  first  edition  of  this  work, 
and  subsequently,  I  placed  in  a  most  conspicuous  position  — 
namely,  at  the  close  of  the  Introduction  —  the  following 
words :  '  I  am  convinced  that  natural  selection  has  been  the 
main  but  not  the  exclusive  means  of  modification.'"  — 
Charles  Darwin,  "The  Origin  of  Species  by  Means  of 
Natural  Selection."  New  York,  reprinted  from  the  Sixth 
London  Edition,  The  Home  Library,  pp.  495-496. 


276     THE  FITNESS  OF  THE  ENVIRONMENT 

orderly  results  of  law,  or  else  we  shall  have  to 
turn  them  over  to  final  causes  ^  and  the  phi- 
losopher. 

There  is,  in  truth,  not  one  chance  in  count- 
less millions  of  millions  that  the  many  unique 
properties  of  carbon,  hydrogen,  and  oxygen, 
and  especially  of  their  stable  compounds 
water  and  carbonic  acid,  which  chiefly  make 
up  the  atmosphere  of  a  new  planet,  should 
simultaneously  occur  in  the  three  elements 
otherwise  than  through  the  operation  of  a 
natural  law  which  somehow  connects  them 
together.  There  is  no  greater  probability 
that  these  unique  properties  should  be  with- 
out due  cause  uniquely  favorable  to  the 
organic  mechanism.  These  are  no  mere  acci- 
dents ;  an  explanation  is  to  seek.  It  must  be 
admitted,  however,  that  no  explanation  is  at 
hand. 

For  the  coincidence  of  properties  itself  a 
rational  explanation  based  upon  known  laws 
of  nature  is  perhaps  conceivable.  Attention 
has  already  been  called  to  the  interconnection 
of  such  properties  as  latent  heat  of  vaporiza- 
tion, thermal  conductivity,  molecular  vol- 
ume, the  value  of  the  van  der  Waals  constant  a, 

^  Bacon  compared  final  causes  to  vestal  virgins.  "Like 
them,"  he  says,  "thej^  are  dedicated  to  God,  and  are  barren." 
- — "The  Advancement  of  Learning,"  Book  II,  p.  142. 


LIFE  AND  THE   COSMOS  277 

the  dielectric  constant,  and  ionizing  power. 
Further,  it  is  of  course  most  probable  that 
numerous  other  properties  are  necessarily 
associated  with  these ;  and  finally  it  is  not 
surprising  that  elements  of  low  atomic  weight, 
which  become  concentrated  in  the  atmos- 
phere on  account  of  the  small  specific  gravity 
of  their  gases,  should  possess  unusual  proper- 
ties, like  high  specific  heat,  or  if  one  property 
leads  to  another,  many  unusual  properties. 
Be  that  as  it  may,  chemical  science  is  still 
a  very  long  way  from  accounting  for  the  simul- 
taneous occurrence  of  the  various  character- 
istics of  w^ater,  especially  if  we  include  such 
things  as  heat  of  formation,  solvent  power, 
the  process  of  hydrolytic  cleavage,  the  degree 
of  solubility  of  carbon  dioxide,  the  anomalous 
expansion  on  cooling  near  the  freezing  point, 
etc. 

There  is,  in  fact,  exceedingly  little  ground 
for  hope  that  any  single  explanation  of  these 
coincidences  can  arise  from  current  hypotheses 
and  laws.  But  if  to  the  coincidence  of  the 
unique  properties  of  water  we  add  that  of  the 
chemical  properties  of  the  three  elements,  a 
problem  results  under  which  the  science  of 
to-day  must  surely  break  down.  If  these 
taken  as  a  whole  are  ever  to  be  understood,  it 
will  be  in  the  future,  when  research  has  pene- 


278     THE  FITNESS   OF  THE  ENVIRONMENT 

trated  far  deeper  into  the  riddle  of  the  prop- 
erties of  matter.  Nevertheless  an  explana- 
tion cognate  with  known  laws  is  conceivable, 
and  in  the  light  of  experience  it  would  be 
folly  to  think  it  impossible  or  even  improbable. 

Such  an  explanation  once  attained  might, 
however,  avail  the  biologist  little;  for  a 
further  problem,  apparently  more  difficult,  re- 
mains. How  does  it  come  about  that  each  and 
all  of  these  many  unique  properties  should 
be  favorable  to  the  organic  mechanism,  should 
fit  the  universe  for  life  ?  And  for  the  answer 
to  this  question  existing  knowledge  provides, 
I  believe,  no  clew.^  _ 

Thus  regarded,  our  new  form  of  the  old 
riddle  appears  twofold,  and,  on  that  account, 
for  the  present  the  more  unanswerable.  There 
is  but  one  immediate  compensation  for  this 
complexity ;  a  proof  that  somehow,  beneath 
adaptations,  peculiar  and  unsuspected  relation- 
ships exist  between  the  properties  of  matter 
and  the  phenomena  of  life ;  that  the  process 
of  cosmic  evolution  is  indissolubly  linked 
with  the  fundamental  characteristics  of  the 
organism;     that    logically,    in    some    obscure 

^  The  great  difficulty  appears  to  be  that  there  is  here  no 
possibility  of  interaction.  In  our  solar  system,  at  least,  the 
fitness  of  the  environment  far  precedes  the  existence  of  the 
living  organisms. 


LIFE   AND   THE   COSMOS  279 

manner,  cosmic  and  biological  evolution  are 
one.  In  short,  we  appear  to  be  led  to  the 
assumption  that  the  genetic  or  evolutionary 
processes,  both  cosmic  and  biological,  when 
considered  in  certain  aspects,  constitute  a 
single  orderly  development  that  yields  results 
not  merely  contingent,  but  resembling  those 
which  in  human  action  we  recognize  as  pur- 
poseful. For,  undeniably,  two  things  which 
are  related  together  in  a  complex  manner  by 
reciprocal  fitness  make  up  in  a  very  real  sense 
a  unit,  —  something  quite  different  from  the 
two  alone,  or  the  sum  of  the  two,  or  the  re- 
lationship between  the  two.^  In  human  af- 
fairs such  a  unit  arises  only  from  the  effective 
operation  of  purpose. 

Now  it  is  most  clearly  evident  from  the 
experience  of  centuries  that  ordinary  teleology 
is  dangerous  doctrine  in  science,  and  in  the 
past,  accidents  apart,  it  has  been  invariably 
sterile.^  A  statement  that  the  legs  have 
been  formed  for  the  purpose  of  locomotion, 
no  doubt  possesses  scientific  validity,  if  it  be 
properly  interpreted.  But  the  real  scientific 
concern   is   for   the   bones   and   muscles,   the 

^  This  appears  logically  to  correspond  with  the  "schop- 
ferische  Synthese"  of  Wundt. 

2  Interesting  discussions  bearing  upon  this  subject  will 
be  found  in  Pearson's  well-known  ''Grammar  of  Science." 


280     THE  FITNESS  OF  THE  ENVIRONMENT 

tendons  and  ligaments  which  are  employed 
in  walking,  and  for  the  evolutionary  process 
by  which  they  have  been  adapted  to  their  use. 
Nevertheless,  biological  science  has  not  been 
able  to  escape  the  recognition  of  a  natural 
formative  tendency,  which  Darwin  identified 
as  the  result  of  natural  selection.  And  now 
it  appears  to  be  necessary  to  postulate  a  like 
tendency  in  the  evolution  of  inorganic  nature. 
We  have  found  that  the  properties  of  the 
environment,  biologically  considered,  present 
the  same  fitness  as  the  properties  of  life.  In 
each  case  the  fitness  results,  at  least  in  part, 
from  an  evolutionary  process.  Through  the 
main  lines  of  later  development  these  are 
both  known,  though  in  both  cases  we  stop 
short,  perhaps  far  short,  of  the  origins  —  the 
origin  of  life  and  the  origin  of  the  universe  — 
if  indeed  they  have  ever  originated.^  Can 
we  then  deny  that  in  the  one  as  in  the  other 
process  there  is  a  tendency,  a  bent,  a  direc- 
tion of  flow  or  development  ?  ^     I  think  not, 

^  It  is  hardly  necessary  to  point  out  that  the  properties 
of  the  elements  are  themselves  quite  free  from  variation  of 
any  sort. 

^  "Alike  in  the  external  and  the  internal  worlds,  the  man  of 
science  sees  himself  in  the  midst  of  perpetual  changes  of  which 
he  can  discover  neither  the  beginning  nor  the  end.  If,  trac- 
ing back  the  evolution  of  things,  he  allows  himself  to  enter- 
tain the  hypothesis  that  the  universe  once  existed  in  a  dif- 


LIFE  AND  THE   COSMOS  281 

and  it  seems  clear  that  the  facts  of  physical 
science  call  for  an  explanation  of  the  tend- 
ency to  fitness  of  the  environment  in  the 
same  way  that  formerly  the  facts  of  biologi- 
cal science  called  for  an  explanation  of  the 
tendency  to  fitness  of  the  organism. 

To  postulate  such  a  tendency  is,  however, 
in  itself  rather  a  philosophical  than  a  scientific 
act,  and  so,  too,  must  be  conjecture  regarding 
the  origin  of  fitness.  It  is  open  to  any  one 
who  may  be  so  minded  speculatively  to  enrich 
this  tendency  with  characteristics  of  any  sort. 
He  may  follow  the  lead  of  M.  Bergson  and 
call  it  impetus,  with  all  which  that  term  now 
implies,  or  he  may  turn  to  natural  theology 
and  regard  it  as  proof  of  supernatural  purpose 
and  design,  or  he  may  find  a  model  for  teleolog- 
ical  views  in  many  other  quarters.  But  one 
thing  is  certain,  no  such  discussion,  be  it  ever 
so  important  to  the  philosopher  or  the  theo- 
logian, can  directly  contribute  to  scientific 
knowledge  and  comprehension  of  the  under- 
lying phenomena,  which  are  the  sole  positive 
and   certain   knowledge   of   the   subject   that 

fused  form,  he  finds  it  utterly  impossible  to  conceive  how  this 
came  to  be  so;  and  equally,  if  he  speculates  on  the  future, 
he  can  assign  no  limit  to  the  grand  succession  of  phenomena 
ever  unfolding  themselves  before  him."  —  Herbert  Spencer, 
"First  Principles."  New  York,  reprinted  from  the  Fifth 
London  Edition,  1880.     The  Home  Library,  p.  57. 


282      THE  FITNESS  OF  THE  ENVIRONMENT 

we  possess.  For  these  facts  an  explanation  of 
a  different  sort  would  be  necessary,  some- 
thing logically  resembling  natural  selection, 
a  natural  process  acting  automatically  through 
the  properties  of  matter  and  energy,  and 
never  overstepping  the  limits  of  matter  and 
energy,  space  and  time;  neither  supernatural 
nor  metaphysical,  but  purely  mechanistic. 
Lacking  any  indication  of  what  such  an  expla- 
nation may  be,  or  how  it  is  to  be  sought,  we 
shall  do  well  to  turn  to  other  considerations. 

II 

VITALISM 

All  the  skill  of  trained  biologists,  multi- 
plying and  refining  our  knowledge  of  the 
forms  of  life,  has  even  yet  not  availed  to  make 
clear  the  fundamental  ideas  of  the  science. 
Complexity  exists  here  in  the  very  nature 
of  the  case,  and  here,  if  at  all,  the  complete 
subjugation  of  natural  phenomena  to  physi- 
cal science  may  be  expected  to  fail. 

In  an  earlier  chapter  the  painful  advance  of 
physics  and  chemistry  into  the  domain  of 
biology  has  been  sketched,  and  it  was  then 
shown  how  progress  is  beset  with  well-nigh 
insuperable  obstacles.  Thus  it  is  that  bio- 
logical  thought  has    never    attained  to    that 


LIFE  AND   THE   COSMOS  283 

finality  which  appears,  at  least  by  contrast, 
to  characterize  the  greater  body  of  opinions 
in  physical  science. 

In  particular  two  extreme  views,  though 
often  commingled,  have  continually  striven 
for  the  mastery.  The  one  of  these,  purely 
scientific  and  wholly  positive,  declares  the 
phenomena  of  life  to  be,  while  partly  unknown, 
ultimately  knowable  as  manifestations  of 
matter  and  energy.  According  to  this  view 
life  is  a  mechanism  and  nothing  more,  in  its 
positive  scientific  aspects  at  least.  Without 
necessarily  denying  such  assertions,  the 
other  view  sees  the  unique  properties  of  life 
to  be  dependent  upon  an  equally  unique 
force  or  tendency,  operating  in  or  through 
its  physico-chemical  organization.  Either 
there  is  a  peculiar  vital  force ;  or  there  is 
manifest  in  the  organism  a  peculiar  tendency ; 
or  at  any  rate  life  patently  follows  the  path 
into  which  it  w^as  propelled  by  an  original 
impetus,  peculiar  to  life,  unknown  in  other 
phenomena.  All  such  views  inherently  par- 
take of  metaphysics,  and  have,  therefore, 
ever  aroused  most  determined  opposition 
among  the  more  orthodox  devotees  of  science. 

Descartes  appears  to  have  been  the  first 
person  to  adopt  the  modern  scientific  attitude 
toward  life,  and  from  him  a  very  large  pro- 


284      THE  FITNESS  OF  THE   ENVIRONMENT 

portion  of  French  biologists,  as  well  as  those 
of  other  nations  like  Huxley  and  Du  Bois- 
Reymond,  derive  their  philosophical  views 
concerning  their  science.  Descartes  per- 
ceived, apparently  the  first  among  the  mod- 
erns, that  the  scientific  explanation  of  vital 
phenomena  must  be  a  physical  one,  in  terms 
of  matter  and  motion.  Far  in  advance  of 
his  time  he  applied  such  ideas  to  the  nervous 
system,  thereby  establishing  the  nature  of 
reflex  action  and  invading  the  very  citadel 
of  animism.  Outside  natural  science,  how- 
ever, Descartes  was  far  from  being  a  mechan- 
ist. Since  the  early  seventeenth  century  the 
conflict  between  vitalism  and  mechanism 
has  ranged  over  the  whole  field  of  biology,  and 
its  history  is  most  complicated.  After  Des- 
cartes, Lavoisier,  by  his  studies  of  combustion 
within  and  without  the  body,  made  the  next 
very  important  step.  He  was  then  followed 
by  Liebig,  Wohler,  and  a  host  of  later  chem- 
ists. 

In  the  main  the  growth  of  exact  science  has 
steadily  delivered  over  one  vitalistic  strong- 
hold after  another  to  the  mechanists.  And 
though  in  the  first  flush  of  triumph  mechan- 
ism has  sometimes  seemed  to  gain  more  in  a 
particular  engagement  than  later  proved  to 
be  the  case,  vitalism  has  perhaps  not  had  a 


LIFE  AND   THE   COSMOS  285 

positive  success  in  three  centuries.  Such  a 
history  no  doubt  depends  upon  the  very  na- 
ture of  the  situation ;  upon  the  inherent  and 
inevitable  weakness,  within  the  domain  of 
science,  of  vitaHstic  views. 

Experience  seems  to  show  that  the  only  kind 
of  hypothesis  which  can  find  conclusive  scien- 
tific support,  or  sound  basis  in  the  phenomena 
of  matter  and  energy,  is  a  mechanistic  hy- 
pothesis. Exact  and  positive  knowledge  can 
demonstrate  scientifically  the  truth  of  no 
other  hypothesis  with  the  finality  which  char- 
acterizes its  proof  of  a  mechanistic  theory. 
Hence,  so  far  as  it  ventures  into  the  field  of 
science  at  all,  a  vitalistic  theory,  when  attacked 
by  science,  cannot  effectually  avail  itself  of 
the  weapons  of  the  assailant,  and  can  never 
make  a  powerful  counter  attack.  Its  only 
method  consists  in  a  determined  resistance, 
yielding  little  by  little  before  the  advance  of 
positive  knowledge  and  never  gaining  new 
territory,  nor,  except  by  accident,  regaining  / 
what  it  has  lost.  Where  this  process  is  to 
end ;  in  what  respect  and  how  far  life  is  des- 
tined ever  to  remain  a  scientific  riddle,  can 
only  be  surmised. 

The  chief  definitive  triumphs  of  the  mech- 
anistic view  are  two  :  the  elimination  of  vital 
force  and  of  a  belief  in  peculiarity  of  chemical 


286     THE  FITNESS  OF  THE  ENVIRONMENT 

composition  from  organic  chemistry,  through 
the  actual  successes  of  the  laboratory  in  new 
syntheses;  and  the  final  recognition,  based 
upon  understanding  of  the  principle  of  the 
conservation  of  energy,  that,  whatever  else 
"vital  force"  may  be,  it  is  certainly  not 
Jorce,  —  a  form  of  energy.  Thus  limited, 
vitalism  has  been  obliged  to  take  refuge  in  a 
more  restricted  belief;  namely,  that  the  organ- 
ism is  somehow  governed  by  a  directive 
tendency  which,  like  an  architect,  presides 
over  its  development ;  but  that  meanwhile  the 
manifold  processes  of  life  and  evolution  go  on 
within  the  world  of  physical  science  just  as 
the  work  of  the  builder  conforms  to  the  laws 
of  mechanics,  though  following  the  plan  of  the 
architect. 

This  view  has  been  well  stated  by  another 
great  Frenchman,  Claude  Bernard:  "Life 
is  the  directive  idea  or  evolutive  force  of  the 
being ;  .  .  .  but  it  would  be  an  error  to  believe 
that  this  metaphysical  force  operates  after 
the  manner  of  a  physical  force.  .  .  .  The 
metaphysical  evolutive  force  by  which  we 
may  characterize  life  is  useless  to  science, 
because,  existing  apart  from  physical  forces, 
it  can  exercise  no  influence  upon  them.  Hence 
we  must  here  separate  the  world  of  meta- 
physics from  the  world  of  positive  phenomena 


LIFE  AND  THE   COSMOS  287 

which  serves  it  as  foundation,  but  which  has 
nothing  to  contribute  to  it.  .  .  .  Summariz- 
ing, if  we  can  define  Hfe  with  the  help  of  a 
special  metaphysical  conception,  it  is  none 
the  less  true  that  mechanical,  physical,  and 
chemical  forces  are  the  sole  effective  agents  of 
the  living  organism,  and  that  the  physiologist 
has  to  take  account  of  their  action  alone.  We 
shall  say  with  Descartes,  *One  thinks  meta- 
physically, but  one  lives  and  acts  physically.' "  ^ 
Thus  restricted,  vitalism  can  apply  only  to 
formative  processes  and  the  like,  though  the 
vitalist  still  sees  in  the  state  of  the  organism 

^"Claude  Bernard,  'La  Science  Experimen tale,'  3me  ed., 
p.  211 :  'La  vie  est  I'idee  directrice  ou  la  force  evolutive  de 
I'etre ;  .  .  .  mais  I'erreur  serait  de  croire  que  cette  force  meta- 
physique  est  active  a  la  fagon  d'une  force  physique.  ...  La 
force  metaphysique  evolutive  par  laquelle  nous  pouvons 
caracteriser  la  vie  est  inutile  a  la  science,  parce  qu'etant  en 
dehors  des  forces  physiques  elle  ne  pent  exercer  aucune  in- 
fluence sur  elles.  II  faut  done  ici  separer  le  monde  metaphy- 
sique du  monde  physique  phenomenal  qui  lui  sert  de  base, 
mais  qui  n'a  rien  a  lui  emprunter.  .  .  .  En  resume,  si  nous 
pouvons  definir  la  \'ie  a  I'aide  d'une  conception  metaphysique 
speciale,  il  n'en  reste  pas  moins  vrai  que  les  forces  meca- 
niques,  physiques,  et  chimiques,  sont  seules  les  agents  effectifs 
de  I'organisme  vivant  et  que  le  physiologiste  ne  peut  avoir  a 
tenir  compte  que  de  leur  action.  Nous  dirons  avec  Descartes  : 
on  pense  metaphysiquement,  mais  on  vit  et  on  agit  physique- 
ment.' "  —  Merz,  "A  History  of  European  Thought  in  the 
Nineteenth  Century."  Edinburgh  and  London,  1903,  Vol. 
II,  pp.  379-380. 


288     THE  FITNESS  OF  THE  ENVIRONMENT 

effects  of  vitalistic  control  of  its  evolution, 
just  as  we  perceive  in  a  house  not  only  the 
material  structure,  but  the  idea  of  the  archi- 
tect. Further,  the  origin  of  life  itself  remains 
shrouded  in  mystery.  Meanwhile,  for  most 
men  physiology  has  become  merely  biophys- 
ics and  biochemistry,  and  mechanism  is  un- 
doubtedly firmly  established  throughout  every 
department  of  the  science. 

Such  limitations  of  the  vitalistic  hypothesis, 
damaging  though  they  may  be,  do  not  de- 
stroy its  claim  to  consideration  as  a  controlling 
factor  of  the  processes  of  evolution,  embry- 
ology, repair,  etc.,  in  spite  of  the  fact  that 
even  here  it  has  suffered  serious  though  less 
complete  reverses.  In  1859  Darwin's  natural 
selection  offered  itself  as  a  possible  substi- 
tute for  vitalism  in  a  part  or  the  whole  of  this 
field,  and  soon  gained  very  general  accept- 
ance. The  survival  of  the  fittest  has  now 
become  in  the  judgment  of  all  biologists  an 
unquestioned  force  in  the  molding  of  life. 
Therefore,  at  best,  but  a  restricted  scope 
within  its  restricted  field  remains  to  vital- 
ism. 

From  the  earliest  days  of  the  new  hypothesis 
it  has  been  widely  recognized  that  to  accept 
the  survival  of  the  fitt  st  as  one  factor  in  the 
adaptation  of  life  to  its  environment  is  quite 


LIFE  AND   THE   COSMOS  289 

a  different  matter  from  proving  it  to  be  the 
only  force  which  directs  evolution.  An  early 
eulogy  by  Du  Bois-Reymond  upon  the  work 
of  Darwin  clearly  discloses  the  nature  of  the 
situation:  **Here  is  the  knot,  here  the  great 
difficulty  that  tortures  the  intellect  which 
would  understand  the  world.  Whoever  does 
not  place  all  activity  wholesale  under  the  sway 
of  Epicurean  chance,  whoever  gives  only  his 
little  finger  to  teleology,  will  inevitably  arrive 
at  Paley's  discarded  'Natural  Theology,'  and 
so  much  the  more  necessarily,  the  more 
clearly  he  thinks  and  the  more  independent 
his  judgment  .  .  .  the  physiologist  may  define 
his  science  as  a  doctrine  of  the  changes  which 
take  place  in  organisms  from  internal  causes. 
.  .  .  No  sooner  has  he,  so  to  speak,  turned 
his  back  on  himself  than  he  discovers  himself 
talking  again  of  functions,  performances,  ac- 
tions, and  purposes  of  the  organs.  The  possi- 
bility, ever  so  distant,  of  banishing  from  na- 
ture its  seeming  purpose,  and  putting  a  blind 
necessity  everywhere  in  the  place  of  final 
causes,  appears,  therefore,  as  one  of  the 
greatest  advances  in  the  world  of  thought, 
from  which  a  new  era  will  be  dated  in  the 
treatment  of  these  problems.  To  have  some- 
what eased  the  torture  of  the  intellect  which 
ponders  over  the  world-problem  will,  as  long 


290     THE  FITNESS  OF  THE  ENVIRONMENT 

as  philosophical  naturalists  exist,  be  Charles 
Darwin's  greatest  title  to  glory."  ^ 

Recently  the  work  of  de  Vries,  "The  Muta- 
tion Theory,"  has  at  length  set  forth  a  num- 
ber of  trustworthy  observations  of  the  origin 
of  species  in  plants  with  which  natural  selec- 
tion, in  the  restricted  original  sense  at  least, 
can  have  nothing  to  do.  The  origin  of  species 
by  mutation  consists  in  a  sudden  discontinu- 
ous variation,  and  selection,  therefore,  has 
no  opportunity  to  operate  upon  a  series  of 
numerous  minute  variations  which  them- 
selves display  no  tendency  of  any  sort  what- 
ever, in  the  manner  demanded  by  the  Darwin- 
ian hypothesis.^  Hence  it  appears  certain 
that  natural  selection  cannot  be  regarded  as 
completely  master  of  the  situation ;  apart 
from  the  origin  of  life  there  remains  a  lacuna 
in  biology  which  for  the  present  no  existing 
mechanistic  hypothesis  can  fill. 

Moreover,  among  other  things,  the  ordinary 
processes  of  regeneration  and  repair  have 
frequently  been  brought  forward  with  some 
success   as   purposeful    activities   inexplicable 

^  Du  Bois-Reymond,  "Darwin  versus  GalisLniy"  "Reden," 
Vol.  I,  p.  211.  Quoted  from  Merz,  "History  of  European 
Thought  in  the  Nineteenth  Century,"  Vol.  II,  p.  435.  To 
the  same  source  I  am  indebted  for  several  other  quotations. 

2 Hugo  de  Vries,  "The  Mutation  Theory."  Chicago,  2 
vols.,  1909,  1910  (trans.  Farmer  and  Darbishire). 


LIFE  AND   THE   COSMOS  291 

by  natural  selection.^  Thus  Du  Bois-Rey- 
mond:  ''One  of  the  greatest  difficulties  pre- 
sents itself  in  physiology  in  the  so-called  re- 
generative power,  and  —  what  is  allied  to  it 
—  the  natural  power  of  healing ;  this  may  now 
be  seen  in  the  healing  of  wounds,  in  the  delim- 
itation and  compensation  of  morbid  processes, 
or,  at  the  farthest  end  of  the  series,  in  the 
re-formation  of  an  entire  fresh-water  polyp 
out  of  one  of  the  two  halves  into  which  it  had 
been  divided.  This  artifice  could  surely  not 
have  been  learned  by  natural  selection,  and 
here  it  appears  impossible  to  avoid  the  assump- 

^  "Still  less  explicable  in  any  way  thus  far  proposed  are 
certain  remedial  actions  seen  in  animals.  An  example  of 
them  was  furnished  in  §  67,  w  here  '  false  joints '  were  de- 
scribed —  joints  formed  at  places  where  the  ends  of  a  broken 
bone,  failing  to  unite,  remain  movable  one  upon  the  other. 
According  to  the  character  of  the  habitual  motions  there  re- 
sults a  rudely  formed  hinge-joint  or  a  ball-and-socket  joint, 
either  having  the  various  constituent  parts  —  periosteum, 
fibrous  tissue,  capsule,  ligaments.  Now  Darwin's  hypothesis, 
contemplating  only  normal  structures,  fails  to  account  for 
this  formation  of  an  abnormal  structure.  Neither  can  we 
ascribe  this  local  development  to  determinants :  there  were 
no  appropriate  ones  in  the  germ-plasm,  since  no  such  struc- 
ture was  provided  for.  Nor  does  the  hypothesis  of  physi- 
ological units,  as  presented  in  preceding  chapters,  yield  an 
interpretation.  These  could  have  no  other  tendency  than  to 
restore  the  normal  form  of  the  limb,  and  might  be  expected 
to  oppose  the  genesis  of  these  new  parts."  —  Herbert 
Spencer,  "The  Principles  of  Biology,"  Vol.  I.  New  York 
and  London,  1909,  revised  and  enlarged  edition,  p.  362. 


292     THE  FITNESS  OF  THE  ENVIRONMENT 

tion  of  formative  laws  acting  for  a  purpose. 
They  do  not  become  more  intelligible  by  the 
fact  that  the  regeneration  of  mutilated  crys- 
tals, observed  by  Pasteur  and  others,  points 
to  similar  processes  in  inanimate  nature. 
Also  the  ability  of  organisms  to  perfect  them- 
selves by  exercise  has  not  found  sufficient 
appreciation  with  regard  to  natural  selec- 
tion." ' 

To  sum  up,  it  appears  certain  that  at  least 
in  a  few  instances,  and  possibly  quite  generally, 
purposeful  tendencies  exist  in  the  organism 
which  seem  to  be  inexplicable  by  natural  selec- 
tion or  any  other  existing  mechanistic  hypoth- 
esis. It  is  not  too  much  to  hope  that  a  scien- 
tific explanation  of  these  phenomena  in  whole 
or  in  part  may  some  day  be  found  ;  but  mean- 
time they  constitute  the  natural  subject 
of  vitalistic  speculation.  A  field  remains, 
though  limited,  where  the  physical  scientist 
cannot  yet  successfully  subdue  the  vitalist, 
however  strong  his  conviction  of  the  errors  of 
vitalism.^ 

1  Du  Bois-Reymond,  "Reden,"  Vol.  I,  p.  226. 

2  The  indeterminism  which  is  based  uniquely  upon  belief 
in  freedom  of  the  will  appears  to  be  foreign  to  the  present  dis- 
cussion. It  is,  accordingly,  entirely  disregarded  in  the  follow- 
ing considerations.  Hence  the  conclusions  of  the  present  in- 
quiry are  not  to  be  taken  as  cognate  with  such  metaphysical 
hypotheses  as  the  indeterminism  of  Kant  and  Lotze. 


LIFE   AND  THE   COSMOS  293 

Vitalism  therefore  flourislies,  as  the  recent 
remarkable  works  of  Driesch  and  Bergson  tes- 
tify. Of  these  two  authors  the  former  is 
concerned  to  prove  that  pure  mechanism  is 
insufficient  in  biology,  and  that  to  mechanism 
must  be  added  his  entelechies ;  ^  the  latter 
has  gone  bej^ond  the  vitalism  of  earlier  au- 
thors, to  give  his  own  view  of  his  speculations, 
and  introduced  the  idea  of  the  vital  impetus. 

A 

THE  VITALISM  OF  BERGSON 

Upon  analysis  the  theory  of  Bergson 
amounts  to  this,  that  there  is  an  original 
creative  impetus  impelled  upon  life  which,  at 
all  events  in  the  main,  is  responsible  for  the 
course  that  organic  evolution  has  taken. 
To  quote  his  own  words:  "So  we  come  back, 
by  a  somewhat  roundabout  way,  to  the  idea 
w^e  started  from,  that  of  an  original  impetus 
of  life,  passing  from  one  generation  of  germs 
to  the  following  generation  of  germs  through 
the  developed  organisms  which  bridge  the 
interval  between  the  generations.  This  im- 
petus, sustained  right  along  the  lines  of  evo- 
lution among  which  it  gets  divided,  is  the 
fundamental    cause    of    variations,    at    least 

1  Driesch,  "The  Science  and  Philosophy  of  the  Organism." 
London,  1907  and  1908,  two  volumes. 


294     THE  FITNESS   OF  THE  ENVIRONMENT 

of  those  that  are  regularly  passed  on,  that 
accumulate  and  create  new  species.  In  gen- 
eral, when  species  have  begun  to  diverge  from 
a  common  stock,  they  accentuate  their  diver- 
gence as  they  progress  in  their  evolution. 
Yet,  in  certain  definite  points,  they  may 
evolve  identically ;  in  fact,  they  must  do  so 
if  the  hypothesis  of  a  common  impetus  be 
accepted.  This  is  just  what  we  shall  have  to 
show  now  in  a  more  precise  way,  by  the  same 
example  we  have  chosen,  the  formation  of 
the  eye  in  molluscs  and  vetebrates.  The  idea 
of  an  'original  impetus,'  moreover,  will  thus 
be  made  clearer."  ^  .  .  .  "If  life  realizes 
a  plan,  it  ought  to  manifest  a  greater  harmony 
the  further  it  advances,  just  as  the  house 
shows  better  and  better  the  idea  of  the  archi- 
tect as  stone  is  set  upon  stone.  If,  on  the 
contrary,  the  unity  of  life  is  to  be  found  solely 
in  the  impetus  that  pushes  it  along  the  road  of 
time,  the  harmony  is  not  in  front,  but  behind. 
The  unity  is  derived  from  a  vis  a  tergo:  it 
is  given  at  the  start  as  an  impulsion,  not 
placed  at  the  end  as  an  attraction.  In  com- 
municating itself,  the  impetus  splits  up  more 
and  more.  Life,  in  proportion  to  its  progress, 
is    scattered    in    manifestations    which    un- 

^  Bergson,  "Creative  Evolution,"  translated  by  Mitchell. 
New  York,  1911,  pp.  87,  88. 


LIFE  AND  THE   COSMOS  295 

doubtedly  owe  to  their  common  origin  the 
fact  that  they  are  complementary  to  each  other 
in  certain  aspects,  but  which  are  none  the  less 
mutually  incompatible  and  antagonistic."  ^ 

The  contention  of  Bergson  may  be  divided 
into  two  parts  :  a  statement  of  belief  in  an 
original  impetus,  and  his  biological  argu- 
ments in  favor  of  such  a  view.  The  former, 
in  so  far  as  it  is  a  question  exclusively  of  an 
original  impetus,  appears  to  lie  outside  the 
scope  of  science,  in  company  with  speculations 
upon  the  origin  of  the  universe ;  the  latter, 
because  it  deals  with  the  subject-matter  of 
science,  is  open  to  scientific  criticism,  and  from 
the  standpoint  of  the  biologist  is  certainly 
far  from  conclusive.^ 

Bergson's  hypothesis  is,  however,  in  es- 
sence not  less  vitalistic  than  that  of  Driesch. 
Both  philosophers  assume  the  existence  of  a 
special  vital  characteristic,  and  explain  the 
course  which  evolution  has  taken  as  a  result 
of  it.  In  short,  modern  vitalism  consists 
in  postulating  a  directive  tendency  which 
manifests  itself  in  or  through  the  organism 
alone,  and  is  peculiar  to  life. 

^  im.,p.  103. 

2  In  fact,  until  the  mechanistic  operation  of  Bergson's 
impetus  can  be  clearly  perceived,  it  must  remain  scientifically 
an  unsoimd  hypothesis. 


296     THE  FITNESS  OF  THE  ENVIRONMENT 

In  such  speculations  the  properties  of 
matter  and  the  process  of  cosmic  evolution 
have  no  place. ^  Bergson,  indeed,  very  defi- 
nitely, and  it  would  seem  gratuitously,  puts 
aside  cosmic  evolution  and  also,  with  certain 
slight  reservations,  the  properties  of  matter  as 
of  no  essential  consequence  in  organic  evolu- 
tion; e.g.  "This  twofold  result  has  been  ob- 
tained in  a  particular  way  on  our  planet.  But 
it  might  have  been  obtained  by  entirely  dif- 
ferent means.  It  was  not  necessary  that  life 
should  fix  its  choice  mainly  upon  the  carbon 
of  carbonic  acid.  What  was  essential  for  it 
was  to  store  solar  energy ;  but,  instead  of  ask- 
ing the  sun  to  separate,  for  instance,  atoms  of 
oxygen  and  carbon,  it  might  (theoretically 
at  least,  and,  apart  from  practical  difficulties 

^  Driesch,  to  be  sure,  has  considered  the  problem  of  uni- 
versal teleology,  but  unsuccessfully  and  with  obvious  vitalistic 
preconceptions  such  as  individuality.  His  nearest  approach 
to  the  thesis  of  the  present  work  is  to  be  found  in  the  follow- 
ing lines:  "I  do  not  hesitate  to  confess  that,  apart  from 
historical  teleology  relating  to  the  sequence  of  one  state  of  poli- 
tics or  economy  upon  another,  and  apart  from  phylogeny, 
there  seems  to  me  to  be  a  certain  sound  foundation  in  the 
concept  of  the  general  harmony  between  organic  and  inor- 
ganic nature,  a  something  which  seems  to  show  that  nature 
is  nature  for  a  certain  ^purpose.  But  I  confess  at  the  same  time 
that  I  am  absolutely  unable  to  consider  this  purpose  in 
any  other  than  a  purely  anthropomorphic  manner."  —  Z/.c, 
Vol.  II,  pp.  348-349. 


LIFE  AND  THE  COSMOS  297 

possibly  insurmountable)  have  put  forth  other 
chemical  elements,  which  would  then  have  had 
to  be  associated  or  dissociated  by  entirely  dif- 
ferent physical  means.  And  if  the  element 
characteristic  of  the  substances  that  supply 
energy  to  the  organism  had  been  other  than 
carbon,  the  element  characteristic  of  the 
plastic  substances  would  probably  have  been 
other  than  nitrogen,  and  the  chemistry  of 
living  bodies  would  then  have  been  radically 
different  from  what  it  is.  The  result  would 
have  been  living  forms  without  any  analogy 
to  those  we  know,  whose  anatomy  would  have 
been  different,  whose  physiology  also  would 
have  been  different.  Alone,  the  sensori-motor 
function  would  have  been  preserved,  if  not  its 
mechanism,  at  least  in  its  effects.  It  is  there- 
fore probable  that  life  goes  on  in  other  planets, 
in  other  solar  systems  also,  under  forms  of 
which  we  have  no  idea,  in  physical  conditions 
to  which  it  seems  to  us,  from  the  point  of 
view  of  our  physiology,  to  be  absolutely  op- 
posed. If  its  essential  aim  is  to  catch  up 
usable  energy  in  order  to  expend  it  in  explo- 
sive actions,  it  probably  chooses,  in  each 
solar  system  and  on  each  planet,  as  it  does 
on  the  earth,  the  fittest  means  to  get  this 
result  in  the  circumstances  with  which  it  is 
confronted.     That  is  at  least  what  reasoning 


298     THE  FITNESS  OF  THE  ENVIRONMENT 

by  analogy  leads  to,  and  we  use  analogy  the 
wrong  way  when  we  declare  life  to  be  impos- 
sible wherever  the  circumstances  with  which 
it  is  confronted  are  other  than  those  on  the 
earth.  The  truth  is  that  life  is  possible  wher- 
ever energy  descends  the  incline  indicated  by 
Carnot's  law  and  where  a  cause  of  inverse 
direction  can  retard  the  descent  —  that  is  to 
say,  probably,  in  all  the  worlds  suspended 
from  all  the  stars.  We  go  further :  it  is  not 
even  necessary  that  life  should  be  concen- 
trated and  determined  in  organisms  properly 
so  called,  that  is,  in  definite  bodies  present- 
ing to  the  flow  of  energy  ready-made  though 
elastic  canals.  It  can  be  conceived  (although 
it  can  hardly  be  imagined)  that  energy  might 
be  saved  up,  and  then  expended  on  varying 
lines  running  across  a  matter  not  yet  solidified. 
Every  essential  of  life  would  still  be  there, 
since  there  would  still  be  slow  accumulation 
of  energy  and  sudden  release."  ^ 

B 

VITALISM  AND  TELEOLOGY 

These  conclusions  appear  to  be  based  upon 
decisions  regarding  the  essential  physico-chem- 
ical conditions  and  characteristics  of  life  arbi- 

1  Bergson,  I.e.,  pp.  9,55,  9,5^. 


LIFE  AND  THE   COSMOS 

trarily  reached  in  accordance  with  precon- 
ceived views,  and  quite  without  scientific 
justification.  There  is  certainly  no  reason 
to  ascribe  greater  importance  to  energy  than 
to  matter  in  the  vital  processes,  and  in  the 
light  of  the  facts  with  which  the  preceding 
chapters  are  concerned,  such  views  seem 
absurd.  Indeed,  whoever  is  disposed  to  spec- 
ulate about  biological  fitness  —  and  not  even 
the  incomparable  finesse  of  M.  Bergson's  dia- 
lectic can  make  fitness  other  than  the  most 
general  result  of  the  process  of  organic  evolu- 
tion —  must  now  weigh  well  the  cosmic  pro- 
cesses. For,  if  allowance  be  made  for  the 
results  of  natural  selection  in  the  organic 
world,  fitness  of  the  environment  has  the 
greater  claim  to  be  considered. 

The  two  fitnesses  are  complementary ;  are 
they  then  single  or  dual  in  origin  ?  The  simple 
view  would  be  to  imagine  one  common  impe- 
tus operating  upon  all  matter,  inorganic  and 
organic,  through  all  stages  of  its  evolution, 
in  all  its  states  and  forms,  and  leading  to 
worlds  like  our  own  through  paths  apparently 
purposeful  and  really  not  yet  explained. 
Such,  it  seems  to  me,  is  the  natural  hypothesis 
for  the  vitalist  to  adopt.  But  then  vitahsm 
vanishes,  only  teleology  remains;  for  the 
unique    characteristic  of   life  is    gone.     Yet, 


SOO     THE  FITNESS  OF  THE  ENVIRONMENT 

putting  aside  mechanistic  differences,  is  it  not 
now  lost  in  any  case  ?  Has  not  modern  vital- 
ism in  accepting  the  limitation  to  entelechies 
or  impetus  destroyed  itself  ? 

The  situation,  briefly,  seems  to  be  as  fol- 
lows :  two  evolutionary  processes  independ- 
ently result  in  two  complementary  fitnesses; 
hence  they  are  related.  In  the  one  process 
the  origin  of  fitness  is  in  part  explained  by  a 
mechanistic  hypothesis.  Nevertheless,  many 
philosophers,  as  is  their  right,  declare  that  in 
this  process  a  further  extraphysical  influence 
is  to  be  assumed.  But  any  one  who  makes 
such  an  assumption  for  the  one  process  must 
certainly  now  make  it  for  the  other;  thus  he 
will  be  led  to  see  impetus  or  entelechies  every- 
where. Under  these  circumstances  it  may 
be  doubted  if  his  acquaintance  with  the  na- 
ture of  his  impetus  or  entelechies  is  so  inti- 
mate that  he  will  be  able  to  distinguish  the 
inorganic  from  the  organic,  for  he  has  surren- 
dered to  science  all  the  positive  physico-chem- 
ical differences  between  organic  and  inorganic 
bodies  and  processes.  Hence,  unless  he  is  to 
make  an  arbitrary  and  unintelligible  distinc- 
tion, or  to  indulge  in  the  spinning  of  cob- 
webs, his  vitalism  has  ceased  to  be  exclusively 
organic,  in  short  has  ceased  to  be  vitalism  at 
all,  and  has  become  mere  universal  teleology. 


LIFE  AND  THE   COSMOS  301 

III 

COSMIC  EVOLUTION 

But,  for  the  scientist,  these  are  matters 
of  Kttle  moment.  He,  at  least,  is  not  obliged 
to  take  any  stand  concerning  them.  This 
could  hardly  be  better  illustrated  than  by  our 
new  facts  themselves.  For  it  seems  to  be 
clear  that  where  science  is  most  self-sufficient, 
at  the  very  basis  of  physical  science  itself, 
if  anywhere,  teleologj^  is  at  work.  Yet  it  is 
certain  that  physical  science  needs  no  tele- 
ology to  explain  its  phenomena  and  pro- 
cesses. These  are  mechanisms,  and  since 
the  publication  of  Newton's  "Principia"  no 
one  has  seriously  doubted  the  fact.^ 

To-day  there  is  as  little  room  for  doubt  that 
a  complete  description  of  cosmic  evolution  in 
terms  of  matter  and  energy  is  possible;  for 
it  is  sound  scientific  doctrine  that  what  exists 
in  the  finished  solar  system  depends  upon 
what  already  existed  in  the  nebula.  The 
forms  and  states  and  quantities  of  matter 
and  energy  in  the  nebula  determine  the  re- 
sulting solar  system.  Further,  since  both 
nebulse  and  solar  systems    are    common    oc- 

*  Laplace's  reply  to  a  question  of  Napoleon's,  "Why  the 
name  of  God  did  not  occur  in  his  '  Mecanique  celeste,' "  will 
be  recalled :   "Sire,  je  n'ai  pas  besoin  de  cet  hypothese." 


S02     THE  FITNESS  OF  THE  ENVIRONMENT 

currences,  it  is  evident  that  nebulae  them- 
selves are  in  a  general  way  determined  by 
other  antecedent  conditions  and  phenomena, 
which  turn  out  to  be  collisions  between  stars. 
Thus  arises  the  suspicion  that  cosmic  evolu- 
tion may  be  in  truth  a  cyclic  process  which 
had  no  beginning  and  can  have  no  end.^ 
An  alternative  hypothesis  regards  the  pres- 

^  Such  a  view,  until  quite  recently,  was  universally  rejected 
because  it  appeared  to  conflict  with  the  second  law  of  thermo- 
dynamics, —  that  of  the  degradation  of  energy.  But  lately  it 
has  been  put  forth  by  no  less  an  authority  than  Arrhenius, 
who  has  advanced  a  theory  to  explain  away  the  difficulty  of 
the  second  law. 

"The  recognition  of  the  indestructibility  of  energy 
seemed  to  accentuate  the  difficidties  of  the  cosmogonic  prob- 
lems. The  theses  of  Mayer  and  of  Helmholtz,  on  the  man- 
ner in  which  the  Sun  replenished  its  losses  of  heat,  have  had 
to  be  abandoned.  My  explanation  is  based  upon  chemical 
reactions  in  the  interior  of  the  Sun  in  accordance  with  the 
second  law  of  thermodynamics.  The  theory  of  the  'degra- 
dation' of  energy  appeared  to  introduce  a  still  greater  diffi- 
culty. That  theory  seems  to  lead  to  the  inevitable  conclu- 
sion that  the  Universe  is  tending  towards  the  state  which 
Clausius  has  designated  as  'Warme  Tod'  (heat  death),  when 
all  the  energy  of  the  Universe  will  be  uniformly  distributed 
through  space  in  the  shape  of  movements  of  the  smallest 
particles.  That  would  imply  an  absolutely  inconceivable 
end  of  the  development  of  the  Universe.  The  way  out  of  this 
difficulty  which  I  propose  comes  to  this :  the  energy  is  '  de- 
graded' in  bodies  which  are  in  the  solar  state,  and  the  energy 
is  'elevated,'  raised  to  a  higher  level,  in  bodies  which  are  in 
the  nebular  state."  —  Arrhenius,  "Worlds  in  the  Making," 
translated  by  Borns.     New  York  and  London,  1908,  p.  xiii. 


LIFE  AND  THE  COSMOS  303 

ent  form  of  our  universe  as  the  result  of  a 
gradual  evolution  from  an  earlier  unknown 
form,  the  development  of  successive  solar 
systems  being  mere  incidents  of  the  larger 
process,  the  evolution  as  a  whole  directively 
governed  by  the  law  of  the  degradation  of 
energy. 

A 

THE  PERIODIC  SYSTEM 

In  either  hypothesis  the  remarkable  sys- 
tematic relationship  between  the  elements 
which  is  manifest  in  the  periodic  classifica- 
tion has  a  peculiar  place.  If  the  second  hy- 
pothesis be  accepted,  there  seems  to  be  little 
room  for  doubt  that  at  an  early  period  the 
chief  cosmic  process  was  the  evolution  of  the 
elements  themselves ;  and  in  the  first  theory 
the  nebula,  whose  properties  depend  almost 
wholly  upon  chemical  constitution  and  chem- 
ical and  molecular  energy,  occupies  a  unique 
position,  like  the  leaf  in  the  organic  cycle, 
or  spring  among  the  seasons.  Thus,  whether 
or  not  the  periodic  sj^stem  is  to  be  regarded 
as  the  one  remaining  plain  result  of  a  process 
by  which  the  elements  were  evolved,  at  least 
it  takes  precedence  over  the  other  properties 
of  matter,  and  lies  at  the  very  foundation  of 
the  known  processes  of   evolution.     Clearly, 


304     THE  FITNESS  OF  THE  ENVIRONMENT 

no  one  can  doubt  that  upon  the  properties 
of  matter  as  determined  by  the  periodic 
system,  and  upon  the  relative  amounts  of  the 
different  elements,  the  actual  process  of  cos- 
mic evolution  from  nebula  to  solar  system 
is  dependent.^ 

Hence,  in  accordance  with  the  general 
method  of  science,  we  must  assume  that  the 
origin  of  environmental  fitness  lies  at  least 
as  far  back  as  the  phenomena  of  the  periodic 
system,  at  least  as  far  back  as  the  evolution 
of  the  elements,  if  they  were  ever  evolved. 
We  simply  cannot  doubt  that  the  origin  of  a 
body  like  the  earth  depends  exclusively  upon 
chance  plus  the  properties  of  the  elements, 
their  relative  amounts,  the  indestructible 
forces  of  nature,  and  the  other  known  factors 
of  mechanism.  The  perfect  induction  of  phys- 
ical science,  based  upon  each  and  all  of  its 
countless  successes  in  every  department  of 
physics  and  chemistry,  conclusively  proves 
that  the  whole  process  of  cosmic  evolution 
from  its  earliest  conceivable  state  to  the  pres- 
ent is  pure  mechanism.^ 

^  The  same  considerations  apply  to  any  other  scientific 
hypothesis  of  the  genesis  of  the  solar  systein. 

2  Not  only  is  this  proved  by  all  experience  of  physical 
science,  it  has  also  ever  been  the  necessary  working  hypoth- 
esis of  physicists  and  chemists. 


LIFE  AND  THE   COSMOS  305 

B 

TELEOLOGY 

If,  then,  cosmic  evolution  be  pure  mechan- 
ism and  yet  issue  in  fitness,  why  not  organic 
evolution  as  well  ?  Mechanism  is  enough 
in  physical  science,  which  no  less  than  biolog- 
ical science  appears  to  manifest  teleology; 
it  must  therefore  suflfice  in  biology. 

Thus  once  more  we  arrive  at  the  negation  of 
vitalism.  For  this  conclusion  w^e  possess 
two  arguments:  the  argument  that  in  such 
aspects  as  concern  physical  science,  and  apart 
from  differences  scientifically  explicable,  or- 
ganic and  inorganic  phenomena  are  alike,  and 
therefore  a  specifically  vital  teleology  is  un- 
necessary ;  and  the  argument  that  inorganic 
science  unquestionably  has  no  need  of  non- 
mechanistic  teleology.  Hence  we  are  obliged 
to  conclude  that  all  metaphysical  teleology  is 
to  be  banished  from  the  whole  domain  of 
natural  science.^ 

What  then  becomes  of  fitness  ?  Clearly 
there  are  two  logical  possibilities.  Either  there 
exists  an  unknown  mechanistic  explanation  of 
that  common  issue  of  the  organic  and  cosmic 

^  Such  at  least  is  the  simplest  provisional  hypothesis,  and 
the  only  view  which  involves  no  gratuitous  assumptions.  It  is 
therefore  the  one  which  must  now  be  adopted. 


306    THE  FITNESS   OF  THE  ENVIRONMENT 

evolutionary  processes,  or  there  does  not.  If 
such  an  explanation  be  possible,  at  least  it 
must  be  admitted  that  it  is  very  hard  to  con- 
ceive. Yet,  recalling  the  difficulty  before  the 
idea  of  natural  selection  arose  of  imagining  any 
mechanistic  explanation  whatever  of  fitness, 
we  shall  do  well  not  to  decide  against  such  a 
possibility. 

On  the  other  hand,  it  is  conceivable  that  a 
tendency  could  work  parallel  with  mechanism 
without  interfering  with  it,  according  to  a 
view  which  has  been  held  by  such  thorough- 
going mechanists  as  Descartes,  Claude  Ber- 
nard, Virchow,  DuBois-Reymond,  and  many 
another.  Although  I  have  no  intention  of 
here  seeking  a  choice  between  these  two  hy- 
potheses, being  in  fact  convinced  that  now, 
at  all  events,  no  choice  is  scientifically  possi- 
ble, and  doubting  if  properly  speaking  they  are 
alternatives  at    all,^   I   do  feel    concerned  to 

^  "Either  the  multitudinous  kinds  of  organisms  which  now 
exist,  and  the  far  more  multitudinous  kinds  which  have  existed 
during  past  geologic  eras  have  been  from  time  to  time  sep- 
arately made,  or  they  have  arisen  by  insensible  steps,  through 
actions  such  as  we  see  habitually  going  on.  Both  hypotheses 
imply  a  Cause.  The  last,  certainly  as  much  as  the  first, 
recognizes  this  Cause  as  inscrutable.  The  point  at  issue  is, 
how  this  inscrutable  Cause  has  worked  in  the  production  of 
living  forms.  This  point,  if  it  is  to  be  decided  at  all,  is  to  be 
decided  only  by  examination  of  evidence.  Let  us  inquire 
which  of  these  antagonistic  hypotheses  is  most  congruous 


LIFE  AND  THE  COSMOS  307 

remove  from  the  latter  view,  if  I  may,  some  of 
the  objections  which  are  commonly  raised 
against  it  in  scientific  circles,  conscious  that 
in  this  attempt  I  am  overstepping  the  bound- 
aries of  natural  science. 

It  is  evident  that  a  perfect  mechanistic 
description  of  the  building  of  a  house  may  be 
conceived.  Within  the  world  of  physical 
science  the  whole  process  is  logically  complete 
without  consideration  of  the  architect's  de- 
sign and  purpose.  Yet  such  design  and 
purpose,  whether  or  not  in  themselves  of 
mechanistic  origin,  are  at  one  and  the  same 
time  determining  factors  in  the  result,  and 
nowise  components  of  the  physical  process. 
Now  it  seems  clear  that  a  similar  effect  of  a 
tendency  working  steadily  through  the  whole 
process  of  evolution  is  also  at  least  conceive- 
able,  however  small  its  bearing  upon  science, 
provided,  like  time  itself,  it  be  a  perfectly 
independent  variable,  making  up,  therefore, 
with  time  the  constant  environment,  so  to 
speak,  of  the  evolutionary  process.  The  tend- 
ency must  not  be  demonstrable  either  by 
weighing  or  by  measuring,  else  it  would 
amount  to  an  interference  within  the  mech- 

with  established  facts."  —  Herbert  Spencer,  "The  Prin- 
ciples of  Biology."  New  York  and  London,  1909,  Vol.  I, 
revised  and  enlarged  edition,  p.  416. 


308    THE  FITNESS  OF  THE  ENVIRONMENT 

artistic  process,  and  it  must  not  be  itself 
liable  to  any  kind  of  variation  whose  detec- 
tion would  directly  reveal  it.  Where  then 
can  the  origin  of  such  a  tendency  be  located? 
Why  clearly,  if  we  accept  the  induction  in 
favor  of  mechanism,  only  where  Bergson  has 
shrewdly  placed  his  vital  impetus,  at  the  very 
origin  of  things,  just  before  mechanism  begins 
to  act.  In  short,  our  new  teleology  cannot 
have  originated  in  or  through  mechanism, 
but  it  is  a  necessary  and  preestablished  asso- 
ciate of  mechanism.  Matter  and  energy  have 
an  original  property,  assuredly  not  by  chance, 
which  organizes  the  universe  in  space  and 
time. 

This  is  in  very  truth  a  metaphysical  doc- 
trine; but  it  has  strong  claims  to  sympa- 
thetic regard  from  men  of  science.  In  the 
first  place,  it  leaves  mechanism  with  the 
perfectly  free  hand  which  that  process  has 
undoubtedly  earned  in  the  world  of  phe- 
nomena. Secondly,  it  does  but  add  one  further 
riddle,  and  that  an  old  and  familiar  one,  to 
those  two  already  tacitly  recognized  by  most 
scientists :  the  existence  of  the  universe  and 
the  existence  of  life.  Given  the  universe,  life, 
and  the  tendency,  mechanism  is  inductively 
proved  sufficient  to  account  for  all  phenomena. 

The  existence  of  the  universe,  on  the  other 


LIFE  AND   THE   COSMOS  309 

hand,  is  no  concern  of  the  scientist.  What- 
ever else  it  may  achieve,  mechanism  can  never 
explain,  cannot  even  face  the  problem  of  the 
existence  of  matter  and  energy.  Within  the 
world  of  science  these  are  conserved  ;  only 
outside  that  world  can  they  have  originated 
or  not  originated.  As  for  the  existence  of 
life,  in  spite  of  our  utter  ignorance,  it  must 
be  admitted  that  a  half  century  has  greatly 
diminished  the  number  of  substantial  biolo- 
gists who  really  look  forward  to  its  scientific 
explanation,  and  the  greatest  chemists  have 
ever  shared  such  a  view.  Liebig  is  reported 
by  Lord  Kelvin  to  have  replied  to  the  ques- 
tion whether  he  believed  that  a  leaf  or  a  flower 
could  be  formed  or  could  grow  by  chemical 
forces,  "I  would  more  readily  believe  that  a 
book  on  chemistry  or  on  botany  could  grow 
out  of  dead  matter. "  ^  Darwin,  too,  once 
said,  *'It  is  mere  rubbish  thinking  at  present 
of  the  origin  of  life ;  one  might  as  well  think 
of  the  origin  of  matter."^  Since  Liebig's 
day  the  chemical  organization  of  the  cell  has 
become  in  scientific  knowledge  vastly  more 
complex  than  it  was  before,  and  I  know  of  no 
biological  chemist  to  whom  the  spontaneous, 

^  Lord  Kelvin,  "On  the  Dissipation  of  Energy,"  Popular 
Lectures,  Vol.  Ill,  p.  464. 
2  Merz,  Vol.  II,  p.  406. 


310     THE  FITNESS  OF  THE  ENVIRONMENT 

that  IS  to  say,  the  mechanistic,  origin  of  a  cell 
is  scientifically  imaginable,^  though  all  believe 
that  once  formed,  cells  exist  as  mechanisms 
in  a  mechanistic  universe.^  Thus  the  chem- 
ist puts  his  mind  at  rest  regarding  the  exist- 
ence of  life,  just  as  the  physicist  calms  his 
regarding  the  existence  of  matter,  simply  by 
turning  his  back  on  the  problem.  Thereby 
he  suffers  nothing  in  his  practical  task  as  a 
man  of  science. 

Returning  now  to  fitness,  we  may  be  sure 
that,  whatever  successes  science  shall  in  future 
celebrate  within  the  domain  of  teleology,  the 
philosopher  will  never  cease  to  perceive  the 
wonder  of  a  universe  which  moves  onward 
from  chaos  to  very  perfect  harmonies,  and, 
quite    apart   from    any   possible   mechanistic 

^  This  is  not  to  express  an  opinion  concerning  the  problem 
of  abiogenesis;  all  admit  that  we  cannot  disprove  such  a 
theory.  But  while  biophysicists  like  Professor  Schafer  follow 
Spencer  in  assuming  a  gradual  evolution  of  the  organic  from 
the  inorganic,  biochemists  are  more  than  ever  unable  to  per- 
ceive how  such  a  process  is  possible,  and  without  taking  any 
final  stand  prefer  to  let  the  riddle  rest.  But  if  life  has 
originated  by  an  evolutionary  process  from  dead  matter, 
that  is  surely  the  crowning  and  most  wonderful  instance  of 
teleology  in  the  whole  universe. 

2  See,  for  instance,  F.  Hofmeister,  "Die  Chemische  Organ- 
isation der  Zelle,"  Vieweg,  Brunswick,  1901,  and  Alsberg, 
"Mechanisms  of  Cell  Activity,"  Science,  pp.  97-105,  July  28, 
1911. 


LIFE  AND  THE  COSMOS  311 

explanation  of  origin  and  fulfillment,  to  feel  it 
a  worthy  subject  of  reflection.  From  this  point 
of  view,  however,  science  need  expect  no  inter- 
ference, but  without  any  last  vestige  of  former 
shackles  may  pursue  the  search  after  mechan- 
istic explanations  of  all  natural  phenomena.^ 

At  length  we  have  reached  the  conclusion 
which  I  was  concerned  to  establish.  Science 
has  finally  put  the  old  teleology  to  death. 
Its  disembodied  spirit,  freed  from  vitahsm 
and  all  material  ties,  immortal,  alone  lives 
on,  and  from  such  a  ghost  science  has  noth- 
ing to  fear.  The  man  of  science  is  not  even 
obliged  to  have  an  opinion  concerning  its 
reality,  for  it  dwells  in  another  world  where 
he  as  scientist  can  never  enter. 

^  "An  evolution  is  a  series  of  events  that  in  itself  as  series 
is  purely  physical,  —  a  set  of  necessary  occurrences  in  the 
world  of  space  and  time.  An  egg  develops  into  a  chick ; 
a  poet  grows  up  from  infancj^ ;  a  nation  emerges  from  bar- 
barism ;  a  planet  condenses  from  the  fluid  state,  and  develops 
the  life  that  for  millions  of  years  makes  it  so  wondrous  a  place. 
Look  upon  all  these  things  descriptively,  and  you  shall  see 
nothing  but  matter  moving  instant  after  instant,  each  con- 
taining in  its  full  description  the  necessity  of  passing  over  into 
the  next.  Nowhere  will  there  be,  for  descriptive  science, 
any  genuine  novelty  or  any  discontinuity  admissible.  But 
look  at  the  whole  appreciatively,  historically,  synthetically, 
as  a  musician  listens  to  a  symphony,  as  a  spectator  watches 
a  drama.  Now  you  shall  seem  to  have  seen,  in  phenomenal 
form,  a  story."  —  Royce,  "The  Spirit  of  Modern  Philosophy.'* 
Boston  and  New  York,  1896,  8th  ed.,  p.  425. 


312     THE  FITNESS  OF  THE  ENVIRONMENT 

I  cannot  hope  to  have  provided  more  than 
a  very  imperfect  illumination  of  certain  as- 
pects of  teleology  in  this  venture  upon  the 
foreign  field  of  metaphysics,  and  I  should 
wish  to  be  understood  as  very  doubtful  of  my 
success  in  stating  what  seem  to  me  some  of 
the  philosophical  conclusions  to  be  drawn 
from  the  fitness  of  the  environment. 

There  is,  however,  one  scientific  conclusion 
which  I  wish  to  put  forward  as  a  positive  and, 
I  trust,  fruitful  outcome  of  the  present 
investigation.  The  properties  of  matter  and 
the  course  of  cosmic  evolution  are  now  seen 
to  be  intimately  related  to  the  structure  of 
the  living  being  and  to  its  activities;  they 
become,  therefore,  far  more  important  in 
biology  than  has  been  previously  suspected. 
For  the  whole  evolutionary  process,  both  cos- 
mic and  organic,  is  one,  and  the  biologist  may 
now  rightly  regard  the  universe  in  its  very 
essence  as  biocentric. 


INDEX 


Absorption  coefficient,  136-138. 

tables,  137. 
Acetylene,  200. 
Acidity,  140,  142,  143. 
Acids,  144,  157,  212,  213,  216,  217. 
Adaptation,  5,  36,  66,   156,  274. 
Adsorption,  128,  129,  130. 
Air,  135. 

tables,  135. 
Alcohols,  212. 
Algol,  46,  47. 

Alkalinity,  142,  143,  155,  167-170, 
188 

blood,  155-159. 

sea  water,  167-170. 

table,  169. 
Ammonia,  66,  110,  263,  264. 
Analysis  of  evidence,  250-253. 
Animism,  284. 
Astronomy,  38-49. 
Asymmetric  carbon  atom,  223. 
Atlantic,  167,  168. 
Atmosphere,  55-60,  134,  135. 

tables,  135. 
Atomic  volume,  10,  11. 

curve,  11. 
Atomic  weights,  14. 
Avogadro's  Hypothesis,  177. 

Balanced  solutions,  175. 
Baltic,  168. 

Bicarbonates  in  blood,  157. 
Biocentric    point    of    view,    110, 

312. 
Biological  chemistry,  193. 
Black  Sea,  168,  169. 
Blood,    115,    116,    153,    155-158, 
161. 
alkalinity,  155-158,  187. 
serum,  116. 

tables,  116,  187. 
Boron,  265. 


Bosphorus,  168. 
Bottom  water,  166. 
Boyle's  Law,  177. 
Bromine,  209. 

Calcium  carbonate,  172,  173. 

Calorie,  81. 

Cane  sugar,  159. 

Capillary  action,  78,  126,  127. 

Carbohydrates,  218,  222-232. 

complexity  of  reactions,  229. 

instability,    223-226. 

mutarotation,  223. 

photosynthesis,  227-229. 
Carbon,  55,  56,  64,  211,  245. 

constituent  of  environment,  64. 

in  stars,  55,  56. 

source  of  energy,  245. 

unique  chemical  properties,  211. 
Carbon  chains,  210. 
Carbon  compounds,  66,  193,  194, 

245. 
Carbon     dioxide.      Chapter     IV 
(133-163),  56,  61,   62,  63, 
64,  65,  66. 

absorption  coefficient,  136-140. 

acidity,  140-163. 

atmospheric,  134,  135. 

distribution,  138,  139. 

excretion,  139,  140. 

in  sea  water,  170. 

metabolism,  132,  133. 

necessary  component  of  atmos- 
phere, 56,  61,  62. 

regulates  neutrality,  147. 

solubility,  136-140. 
Carbonic  acid,  see  Carbon  dioxide. 
Celestial  mechanics,  153. 
Characteristics  of  life,  30-35. 

incompleteness  of,  34. 
Chemical    properties,     206,    207, 
209-222,  254,  255. 


313 


314 


INDEX 


Chemistry,  Chapter  VI  (191-248). 

inorganic,  237-243. 

organic,  191-237. 
Chlorine,  209,  242. 
ChlorophyU,  230,  240,  241. 
Circulation  of  water,  91,  180-182. 
Classification     of     organic   com- 
pounds, 212. 
Climate,  87. 

table,  87. 
Coagulation,  90. 
Coal,  57. 

Colloids,  77,  123,  128,  129,  130. 
Color,  263. 
Combustion,  25. 
Complexity,  31. 
Compounds  of  carbon,  hydrogen, 

and  oxygen,  202-207. 
Compressibility,  262. 
Concentration,  171. 
Conditions,  31,  164-180. 
Conservation  of  energy,    15,    18, 

25,  286. 
Constitutional  formulas,  197-207. 
Contraction,  see  Expansion. 
Copper,  241. 

Cosmic  evolution,  131,  301-312. 
Cosmography,  39,  60,  61. 
Cycle  of  matter,  26-28. 
Cyclic  compounds,  200,  201,  219. 

Degradation  of  energy,  18. 

Design,  85,  307. 

Dew,  105. 

Diabetic  coma,  157. 

Dielectric  constant,  121,  122,  125. 

table,  125. 
Digestion,  232. 
Distribution,  128,  138. 
Double  bonds,  200. 
Dulong  and  Petit's  Law,  82, 83,  84. 
Durability,  31. 
Dynamics,  2,  16. 

Earth,  61-63. 
Electricity,  256. 
Electro-physiology,  124. 
Elements,  72,  73. 
chemical,  9-15. 

figure,  11. 

table,  14. 


Energy,  15-19,  68,  69,  237. 
Entelechy,  293,  300. 
Environment,    Chapter    II    (38- 
71),  8-21,  32,  33,  183-190. 
possible,  49-51. 

primary  constituents  of,  61-63. 
Enzymes,  90,  230,  231. 
Ethane,  198. 
Ethylene,  200. 

Evaporation,  92,  97,  98,  101,  102, 
103,  127,  174,  180. 
latent  heat  of,  97-103. 
table,  99,  100. 
Evolution,  278,  279. 
Excretion,  139. 
Exhaustiveness  of  treatment,  253- 

267. 
Expansion,  106-110. 
table,  107. 

Fauna,  186. 

Figure,  the  atomic  volume  curve, 

11. 
Final  causes,  4,  276. 
Fitness,    Chapter   I    (1-37),   4-8, 
65,  66,  69,   131,   132,  266, 
267,  274-282,  305-307. 
explained  by  Darwin,  5. 
Flora,  186. 
Form,  24,  26,  32. 
Formaldehyde,  225,  228,  229. 
Freezing  point,  93,  94,  178,  179. 
depression,  178,  179. 

tables,  178,  179. 
table,  94. 
Frog's  muscle,  262. 
Fusion,  92-94. 

latent  heat,  92-97. 
table,  95,  96. 

Gastric  juice,  242. 
Gay-Lussac's  Law,  177. 
Geology,  73,  112,  173. 
Geophysics,  52-55. 
Germanium,  12,  13. 

table,  13. 
Glucose,  160,  222-227. 

formation,  227. 

mutarotation,  223. 

reactions,  224-226. 
Glycerophosphoric  acid,  241,  242. 


INDEX 


315 


Glycogen,  234. 
Gulf  Stream,  182. 

Haemocyanine,  241. 

Hsemoglobin,  241. 

Heat  of  combustion,  69,  217,  245, 

246. 
table,  245. 
Heat  of  formation,  244-247. 

tables,  244,  247. 
Heat  of  reaction,  235,  236,  243- 

247. 
table,  236. 
Helium,  41,  42,  58. 
Henry's  Law,  137. 
Herring,  175. 
Heterogeneous    equilibrium,   151, 

158. 
Hexakontane,  210. 
Hexanes,  198,  199. 
Hippuric  acid,  234. 
Histidine,  226. 

Homogeneous  equilibrium,  149. 
Hydrocarbons,  197-202. 
Hydrogen,    55,    56,    58,    64,    211, 

237-243,  245. 
ions,  141-143,  169. 

in  sea  water,  table,  169. 
Hydrogen  sulphide,  152. 
Hydrolysis,  159,  232-237. 
Hydroxyl  ions,  141-143. 

Impetus,  281,  293-295. 
Inactivity,  147. 
Inorganic  chemistry,  237-243. 
Instability,  221. 
Interstellar  space,  50. 
Iodine,  209,  242. 
Ionization,  118-126,  155. 

constant,  140-163,  216. 
tables,  144,  216. 

water,  141-143. 
Iron,  241. 

Lactic  acid,  225. 

Latent  heat,  92-105,  125. 

tables,  95,  96,  99,  100. 
Lesina,  166. 

table,  166. 
Levulose,  224-226. 
Life,  origin  of,  288,  309,  310. 


Light,  256. 
Limestone,  136. 

Lobry   de   Bruyn's   phenomenon, 
224. 

Magnesium,  241. 

Magnetism,  256. 

Mannose,  224-226. 

Marmora,  Sea  of,  168. 

Mass  Law,  152. 

Matter,  8-15. 

Mechanics,  255,  256. 

Mechanism,  282-300,  301. 

Mediterranean,  167,  168,  174. 

Melting,  see  Fusion. 

Melting  point,  see  Freezing  point. 

Metabohsm,    24-28,    32,    33,    35, 

158. 
Meteorology,  57,  58,  73-75. 
Methane,  197. 
Methyl  formate,  233,  234. 
Methyl  glyoxal,  225,  226. 
Methyl  imidazol,  226. 
Mobility,  139,  184. 
Mobilization,  115,  141. 
Molecular  constitution,  28,   196- 

210. 
Molecular  volume,  125. 
Morphology,  23. 
Mutarotation,  223,  224. 
Mutation,  290. 

Natural    selection,    4,    156,    274, 

280,  288. 
Natural  theology,  85,  281,  289. 
Nebulae,  48-50. 
Neptunism,  73. 
Neutrality,  142,  143,  146. 

regulation,  143-162. 
tables,  148,  150. 
Nitrogen,  211. 

compounds  of,  208,  209. 
North  Sea,  168,  169. 
Nucleic  acids,  241. 

Ocean,  Chapter  V  (164-190),  78, 
113,    114,    135,    136,    153- 
155. 
alkahnity,  167-171. 

table,  169. 
as  environment,  183-190. 


316 


INDEX 


Ocean,  concentration,  171-176. 
table,  171. 
currents,  88,  180-182. 
mobility,  180-182. 
osmotic  pressure,  176-179. 

tables,  178,  179. 
regulation  of  conditions,    164- 

180. 
temperature,  165-167. 
tables,  165,  166,  167. 
Oceanography,  165. 
(Edema,  161. 
Optical  activity,  223. 
Order,  1. 
Organic  chemistry,    28-30,    191- 

237. 
Organism,  21-36,  63,  76. 
Osmotic  pressure,  176-180. 
Oxidation,  25,  246,  247. 
Oxygen,  64,  211,  237-243. 

Paleocrystic  ice,  108. 
Panspermia,  50. 

Paraffine  hydrocarbons,  212,  214. 
Partial  pressure,  137. 
Periodic  system,  9,   11,   14,    210, 
211,  303,  304. 

figure,  11. 

table,  14. 
Pharmacological  action,  175. 
Phase  Rule,  257-261. 
Phosphoric  acid,  146,  147,  156. 
Phosphorus,  241,  242. 
Photosynthesis,  27,  227-231. 
Physical  chemistry,  256,  257. 
Physiology,  22,  123,  124. 
Planets,  46,  60. 
Possible  en\'ironments,  49-51. 
Primary  constituents  of  the  en- 

vu-onment,  61-63. 
Propane,  derivatives  of,  203-205. 
Properties  of  matter,  70. 

interconnection,  276,  277. 

omitted,  261,  262. 
Proteins,  156,  242. 
Protoplasm,    26,    129,    130,    153, 

155,  156. 
Purpose,  1,  307. 

Radicals,  211-218. 
Rain,  105. 


Red  Sea,  174. 

Reduction,    227,    228,    231,    244, 

247. 
Reflex  action,  284. 
Regeneration,  290-292. 
Regulation,  31,  164-180,  186,  189. 
Repair,  290-292. 
Respiratory  center,  157. 
Rivers,  113,  172,  180. 
composition,  113. 
table,  113. 

Salinity,  113,  114,  171-175,  187. 

table,  171. 
Salt,  113,  114,  172,  173. 
Sea  urchin,  175. 
Sea  water,  114,  153,  154,  155,  185. 

a  balanced  solution,  175. 
Silicon,  66,  265. 
Skager-Rack,  168. 
Soil,  78,  127. 
Solar  system,  60,  61. 
Solidification,  108. 
SolubHity,  136-138,  140. 

of  carbonic  acid,  136-140. 
Solvent,  68,  79,  111-118,  121. 
Sound,  256. 
Space,  19-21. 

Specific  heat,  67,  68,  80-91. 
Stabmty,  78,  150,  164,  186,  218. 
Stars,  41-44,  50. 
Sugars,  218,  222-232. 
Sulphur,  209,  242. 
Sulphureted  hydrogen,  152. 
Sulphurous  acid,  169. 
Summarj%  267-273. 
Sun,  44-46,  50,  60. 
Surface  temperature,  166. 
Surface  tension,  126-130. 
Sur^-ival  of  fittest,  288. 
Synthesis,  192,  286. 

Tables: 

Absorption  coefficients,  137. 
Alkalinity    and    acidity,     148, 

150. 
Alkalinity  of  sea  water,  169. 
Comparison  of   blood  and  sea 

water,  187. 
Comparison  of  properties,  125. 
Composition  of  air,  135. 


INDEX 


317 


Composition    of    blood    serum, 

116. 
Composition    of     river    water, 

113. 
Composition  of  sea  water,  171. 
Derivatives    of    propane,    203- 

205. 
Elements,  14. 
Expansion  of  water,  107. 
Fitness,  250-252. 
Freezing  point  of  blood  serum, 

178,  179. 
Germanium,  13. 
Heat  conducti\dty,  106. 
Heat  loss  of  dog,  103. 
Heats  of  combustion,  245. 
Heats  of  formation,  247. 
Heats  of  reaction,  236. 
Heats  of  reduction,  244. 
Ionization  constants,  144,  216. 
Latent  heat  of  fusion,  95,  96. 
Latent    heat    of    vaporization, 

99,  100. 
Melting  points,  94. 
Normal  temperatvues,  87. 
Properties  omitted,  261,  262. 
Range  of  temperature,  165,  166, 

167. 
Specific  heats,  81,  83. 
Surface  tension,  126. 
Vapor  tension,  105. 
Teleology-,  279-282,  289,  298-300, 

301,  305-312. 
Temperature,  67,   137,   153,   165, 

166,  167,  170,  188. 
range,  165,  166,  167. 

tables,  165,  166,  167. 
tables,  87,  165,  166,  167. 
Temperature   regulation,   70,    86, 

87,  89,  91,  95,  98,  102,  103, 

109,  167. 
Theory  of  solution,  177,  179. 
Thermal  conductivity,  106,  125. 

table,  106. 
Thermal  properties,  80-110. 


Thermochemistry,  243-248. 
Thermodynamics,  16,  18,  19,  128. 
Time,  19-21. 
Trade  winds,  181. 
Treble  bonds,  200. 

Urea,  192,  234. 
Urine,  117. 

Valence,  196,  197. 
Van  der  Waals's  constant  a,  125. 
Vaporization,  see  Evaporization. 
Vapor  tension,  104,  105. 

table,  105. 
Variable  stars,  46,  47. 
Variety,  68,  207,  220. 
Velocity  of  reaction,  90,  94,  159, 

170,  171. 
Vital  force,  191,  286. 
Vitalism,  282-300,  305. 

of  Bergson,  293-298. 
Volcanoes,  56,  134. 

Water,  Chapter  III  (72-132),  57, 
61-67,  131 ;  transparency, 
100;  as  element,  72,  73; 
universal  importance,  73- 
78 ;  quantity  and  distri- 
bution, 78-79 ;  chemical 
inertness,  79  ;  thermal  prop- 
erties, 80-110;  specific 
heat,  80-91 ;  effect  upon 
temperature,  86-91 ;  latent 
heat,  92-105 ;  evapora- 
tion, 101-104 ;  vapor  ten- 
sion, 104,  105 ;  thermal 
conducti\dty,  106 ;  expan- 
sion, 106-110;  solvent, 
111-118;  ionization,  118- 
126  ;  surface  tension,  126- 
130;  in  soil,  126,  127; 
fitness,  131. 
vapor,  101. 

Weathering,  114,  140. 

Winds,  88,  181. 


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